Boston is a city of neighborhoods, many of which were originally towns in their own rights before being assimilated into the city itself. These neighborhoods still go by their original names and people will often tell you they are from "JP" (Jamaica Plain) or "Eastie" (East Boston) rather than from "Boston." Alternatively, people from the suburbs will tell you they are from Boston when in fact they are not, but live in one of the nearby (or even outlying) suburbs. If in doubt, you can look for "Resident Parking Only" signs which will tell you what neighborhood you are in.
Each neighborhood and neighboring city has more specific listings than what's on this page.
City of Boston
The official limits of the city, or "Boston Proper" as it is sometimes called. It is here where most of the buildings that comprise the city's skyline are located.
East Boston is on a peninsula across Boston Harbor from the main bulk of the city; it's next to Logan Airport.
Charlestown is across the Charles River, on the part of the mainland where Cambridge and Somerville are located. It's where you'll find the Bunker Hill Monument.
The South End, North End, South Boston, and the West End are not the neighborhoods farthest in these respective directions.
The Back Bay is one of the few neighborhoods with a grid-like street network. The cross-streets are named after Massachusetts towns and arranged in alphabetical order: Arlington, Berkeley, Clarendon, Dartmouth, Exeter, Fairfield, Gloucester (pronounced gl-OWW-ster), and Hereford. After Hereford is Massachusetts Avenue (or Mass Ave, as it is commonly known) and then Charlesgate, which marks the boundary of Back Bay. (Trivia fact: the alphabetical streets continue on the far side of Massachusetts Avenue in the Fenway neighborhood, with Ipswitch, Jersey, and Kilmarnock -- but at that point, it's no longer a grid.)
There are also several "districts" you might hear mentioned. "Districts" are generally areas of common interest located within a larger neighborhood:
Though technically speaking not Boston, these cities are in many ways a part of the city and are an essential component to any visit to Boston.