Types of Accommodation
Hostels originally provided dormitory-style budget accommodation to travellers. However, many hostels now provide private single and double rooms in addition to dormitory accommodation.
Many national hostelling organizations have joined together to form Hostelling International (formerly International Youth Hostel Federation), which maintains lists of youth hostels around the world and even takes bookings for some online. Affiliated hostels usually offer a certain minimum standard of lodging and a degree of accountability, although usually the largest risk (in terms of theft) is your fellow travellers, not the management.
Note that in some countries, many hostels are not affiliated with IYHF (eg. Australia). Particularly in poorer countries, the IYHF network may be very limited and possibly even more expensive than alternative accommodations. Also beware of hidden charges: for example, in Scandinavian countries it is typical to charge extra if you do not provide your own bedding.
Hotels provide private serviced rooms for guests. They range from very basic budget-style to extremely luxurious accommodation. Many hotel rooms are double or twin rooms with a smaller additional charge for extra guests.
Bed and Breakfasts and Guesthouses
Bed and Breakfasts (B&Bs) and Guesthouses provide hotel style rooms. However, they are typically smaller residences and you will interact with your hosts and other guests, often eating together and sharing common spaces. Bed and Breakfasts and Guesthouses are more commonly found outside major cities, and many market themselves as providing a "quiet escape".
Many residents of popular holiday areas lease their houses and apartments to tourists. The residence may have been bought specifically for this purpose or the normal occupants may vacate it during some parts of the year. The guests will have full use of the residence, and usually the residence will not be serviced during their stay.
Self-catered rentals are usually cheaper than booking a hotel room for the same length of time. Utilities are normally included in the rental price and electricity and so on (if available) will be connected for your stay.