i Am new to Aosp , i do not where to start, i am doing some task given by our sir, but why it has to be done.

Please some body guide for Aosp Developtment
also, i will more benifical if you can provide me

the list of project or milestone that need to be completed or capture in learnig phase

i did some task like:
build android for emulator
build android for a specific board
making a custum serial service

but all copy pasted form some one

i want a roadmap or milestone which should help me to build the confidence in android