Hi! Did you know that the company behind the operating system you are using is sort of famous for this little thing called a search engine? Crazy, I know.
AOSP is android open source project (thank you Google for letting me know that after typing some words in a box). It is what android as you see it is built from.
AOKP is an open source project by some creative individuals that takes aosp source and modifies it to give the use an enhanced experience. It has lots of toggles and options to customize your device.
3 minutes with Google would have answered all your questions.
Sent from my Nexus 5