Tridion (or SDL Web as it’s called nowadays) allows many extension points. You can extend the content editor GUI, you can extend events, and you can also extend a lot of things on the content delivery side, for example Ambient data claimprocessors, TCDL tag handlers, storage extensions, …
These content delivery extension points are usually written in Java.
This blog post will show you how you can easily add your own configuration files for your code.