A Bitcoin address, or simply address, is an identifier of 27-34 alphanumeric characters, beginning with the number 1 or 3, that represents a possible destination for a Bitcoin payment. Addresses can be generated at no cost by any user of Bitcoin. For example, using Bitcoin-Qt, one can click "New Address" and be assigned an address. It is also possible to get a Bitcoin address using an account at an exchange or online wallet service.
An example of a Bitcoin address is 3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy.
Source:
https://en.bitcoin.it/wiki/Address