what is cache and how many types of Caches are there in XI and what are their puposes?

Ans:Two Types

1.CPA cache(Collaboration profile agreement)
2.Runtime cache

CPA cache: - CPA cache - is your Collaboration profile agreement cache, ie to
mean it will contains the cache copy of all objects created during configuration
time (ID).CPA (Collaboration profile agreement )Cache-mainly for J2EE
engine/Adapter engine.

Runtime Cache:- Runtime cache - it will contain cache copies of all the
objects in XI (IR/ID) and active version of all your objects during runtime.