Git hooks are similar to SVN hooks; you can execute a script at a point in the Git routine. Git hooks are both local and server-side. The local hooks pertain to local activities, like committing, merging, checking out, etc. The server-side hooks deal with receiving pushes from a local client.
The scripts that Git hooks execute are stored in the .git/hooks directory of your project. In every repository there are a collection of sample hooks that you can rename and use as inspiration for your own.
The scripts can be in any language...