Cheap German bus ticket?

I'm currently in germany and someone was telling me something about being able to buy bus tickets in packs from train stations and that they were cheaper than just buying a ticket for one trip. My memory is very fuzzy and I don't remember all the details. Can anyone help me out?
Answers

Percyqted

Go to your nearest Bahnhof and ask there.

The original Peter G

Most German cities sell all service passes for various lengths of time