What is a language binding?

My good friend, Wikipedia, didn't give me a very good response to that question. So:

• What are language bindings?
• How do they work?

Specifically accessing functions from code written in language X of a library written in language Y.

Let's say you create a C library to post stuff to stackoverflow. Now you want to be able to use the same library from Python. In this case, you will write Python bindings for your library.

Also see SWIG: http://www.swig.org