Technical terms

Hi every body!

I'm new in the industry and i'm trying to learn by myself.

So, i've heard of a few technical expressions that i don't really understand.
Could somebody explain them to me or tell me where to learn more about them?

Those are:
- Sequences objectives
- Exotic 3Cs
- LD environments
- Detection system

If anybody can help, that would really be great!!

Thanx