What's ABI?

[Lau <zenith nixstyle net>]

Hi,

        I'm quite often to hear about the terms ABI and API.

        I know that, API stand for Application Programming Interface, right, and it
is the interface of a library; if you are writing a program, just following the API specified by the library 
manual and compile, link.. etc, and it's done, right??

        Then, how about ABI??

Lau