[JackEvans]

What programming language do I need to know to script for SAMP?

[iJokerHD]

I think you can find this information on ******.

[420Scripter]

It's a language called PAWN.
You can learn a bit about it HERE.
If you're trying to learn and have some questions please post your questions HERE.

[Konstantinos]

This might be helpful about the language in general: Pawn Language Guide

About SA:MP Functions/Callbacks and many more: SA-MP Wiki