This article is a travel topic
A passport is a government-issued identification which allows the passenger to travel freely outside his homecountry (subject to regulations of other countries) and receive assistance from officials representing the aliens' homecountry (i.e. in an embassy or consulate) in the country he intends to visit. This is a major requirement for international travel. These are usually complemented by visas, which are issued by the country the alien intends to visit (through an embassy or consulate in the aliens' homecountry) and pasted or stamped in one of the passport pages. Neither document however guarantees entry into another country.
When purchasing tickets over-the-counter for foreign travel, a passport is usually required to be presented to the agent. Within a homecountry, a passport can also be used as identification to obtain certain services such as application for a new bank account.
The first convention on passports was when, in 1920, the League of Nations decided that all passport contain information in French, being the diplomatic language of that era. Today all passports contain information in at least English and French, as well as the official language(s) of the issuing nation (if not English or French).
The cover page includes the word "passport" and the name of the the issuing country in the native language(s) of the issuing country(and possibly a second language, such as English); some sort of national symbol; and special, universal symbol if it is biometric. Additionally, all EU member states have "European Union" (perhaps in another language) above the name of the issuing country.
The information page of the passport records basic information about the passport: its bearer's surname, given names, photo and date and place of birth, validity period, issuing authority, place of issue and passport number. Most passports also contain a request for safe passage and right to consul in event of incarceration. Most passports issued in recent years have a machine-readable strip at the bottom of the page to expedite encoding at the relevant stations (see the relevant section below).
In some countries, the next pages are for amendments where the bearer country's issuing may place travel restrictions, change conditions for travel abroad, or amend the period of validity. In addition, pages may be included which provide helpful legal and practical information for the bearer. For instance a US passport contains 6 pages regarding websites and contacts for various reasons (travel restrictions, treasury restrictions on imports, paying taxes while in a foreign country, registering your stay in a foreign country), common sense subjects (don't be a target, be mindful of security threats, ways to lose citizenship), and important information (loss, theft, destruction, alteration, or mutilation of the passport, what to do in a natural disaster or catastrophic event, etc).
Most of the passport pages are alloted for visas where visas coming from different embassies or consulates are pasted. Stamps from passport control officers of both the bearer's home country and countries visited revealing the history of entry and exit of those countries are also found on these pages.
Depending on the country's practice, Some passports may allow the addition for extra pages. Some countries require 2 blank pages in your passport before you enter the country. If you are running low on blank pages, contact your nearest passport office, embassy, or consulate and they should be able to add extra pages for free or a fee depending on issuing country.
Instead, some couontries may issue a new passport "cross-linked" (or even physically bound) to the old one. The old one must have a blank page for the authority to endorse a cross-link. This is useful not only when a passport is running low on blank pages, but also in cases where the visa outlasts the passport that contains it.
It can be possible for a person to hold multiple passports from a single country at the same time, although not all countries allow this and even for those countries where it is allowed, it is something of a rarity. Not everyone, including some immigration officials in more remote places, knows that it is both possible and legal to have 2 or more passports. If you are off the beaten tracks, it is advisable to only show the passports that are needed for that particular border, as multiple forms of the same ID can look suspicious. Instances where 2nd (or even 3rd) passports can be issued include:
Kinds of passports issued
As the name implies, this passport is typically issued to diplomats as well as high-level government officials. In some cases, bearers of these passports will have different visa requirements from regular passport bearers.
This type of passport is generally issued to government employees for work-related travel. These are often treated like diplomatic passports.
Regular (or tourist) passport
This is the most common type of passport issued. It must meet certain established criteria to be recognized and is allowed for general international travel.
In some countries (e.g. Russia) a local passport is for citizen's domestic use only; for international travel a regular (tourist) passport should be issued. An internal passport often serves to prevent the flow of persons from one region of a country to another, this is often implemented to prevent residents of a volatile region from spreading their conflict to another region.
Many Americans cross the Canadian border daily and new requirements require passports to travel to all nations, including Canada and Mexico. The passport card has the same status as the passport book, but in card form for the convenience of frequent border crossing and is only valid for land and sea travel between the United States and Canada, Mexico, and the Caribbean (sea travel only).
Technology and security
Over the years, the way passports are produced have changed. Passports where the frontpages are handwritten still exist although they are being phased out due to security concerns.
Increasingly in the 90s, machine-readable passports have been introduced where the personal data page is automated. That information is also encoded into 2 strips at the bottom of the page. This helps speed-up lines at most passport control stations as the officers don't need to type-in the most of the entries in their respective fields manually in the computers.
Most nations have implemented biometric passports - a passport containing an RFID chip which contains (depending on issuing country): electronic recording of passport data, a photograph, and/or fingerprints.
Where to apply
Your home country's passport issuing authority, normally under its ministry of foreign affairs (the State Department for U.S.) usually takes care of passport applications, and applicants typically go to their nearest representative or satellite office. Some countries' applications can be initiated online. If you are a resident alien of another country, you can go to your home country's embassy or consulate to apply.
What if I lose it while travelling?
Most people travelling outside of their home country have not had this problem. But a few people have had at least one nightmare about losing their passport. In this event, take a deep breath and contact your embassy ASAP to begin the replacement process. It can often take anywhere from a few days to a couple weeks to get a new passport in a foreign country, depending on your citizenship and your location.
Some countries offer "emergency passports" if you can convince them that you can't wait out the normal turnaround time. These documents usually expire within a year of issue, and often raise eyebrows and slow you down when going through immigration at airports and land borders. It takes a much shorter time, often just hours, to obtain than a full-blown replacement passport. A police report is a good idea and may even be required by your embassy, even if there was no crime involved. And don't forget to bring a couple of passport photos.
Many travellers often carry multiple copies of their passport (and other important documents) when abroad, stashed away in separate locations; folded together in their wallet, in their luggage, or even scanned into a computer. This is especially useful when travelling in areas where risk of loss or theft is high, as it could save you from problems with local authorities, and make a passport easier to obtain, as at least some proof of your identity remains, and other critical information like the passport number. It can also be a good idea to get a copy of your entry stamp and/or visa, so you can quickly provide authorities with proof you are authorised to be in the country in question - although this is mainly an issue in countries with rampant corruption.
Giving your passport to others
In some countries hotels are required to keep photocopies of your passport, if you don't want to trust hotel staff with your passport, e.g. if staff have to leave the hotel premises in order to make a copy, you will be able to provide your own - no need to be overly paranoid, but having staff run across town with a passport worth more than they make in a year, to find the only Xerox in town, might prove too tempting for some people. In any case you should never hand over your passport as a security or guarantee under any circumstances, except as required by law or as a condition of release on bail.
A passport may be treated as a privilege to citizens of the said country. This means the citizen concerned may be required to surrender it to local authorities at certain times such as when they are subject to criminal investigation. Moreover, some passports issued by some countries may expire earlier than usual, and this may indicate that the holder is nearing the required age for conscription.
In some cases, countries with poor or no diplomatic relations may bar the bearers of the other country's passport (or merely having stamps of that other country) from seeking entry. This is the case, for instance, with Israeli passport holders, and sometimes those with just an Israeli stamp, who are usually not permitted to enter most Arab/Islamic states.
For people with dual citizenship remember to be careful on the following issues. If you have two passports issued from two different states, in almost all cases, you must use the passport you enter the country to exit out of. Some countries still do not recognize dual citizenship so you may have some legal trouble using or even just possessing another passport issued from another state. Contact both countries of citizenship before you travel to make sure that you will not arrive on any problems. Sometimes you may even have to travel through the third country to drop off either passport to avoid its being confiscated by the other country claiming you to be its citizen or national.