Think of optionals simply as variables that might contain nil. The only hard part is remember all of the syntax that goes along with declaring optionals, unwrapping them and checking if contain nil before using them.
That will come with time! I highly recommend you download the worksheet to get some extra practice with them. It will help you remember the syntax without having to memorize anything!
This lesson teaches you how classes can "build off" of one another. It's called class inheritance and subclassing and it will save you a ton of time and rewriting of code!
Furthermore, it's used everywhere in the UIKit classes!