Hi!
I really don't what is my proper doubt in it because I don't get what is Shells, orbitals, Principal quantum no, Angular and spin and all... What are they? Why are they? What do they represent??
Sorry for my improper question and Thanks for reading it. Bless you all!

Why are you taking the course? What course is it. If you Google each of the items you note, you will find detailed answers. They all relate to atoms.