Games are all of my professional projects. They are completed, finished games available now on (App) store shelves. They say you can't put a price on passion, but looking here it would somehow be a little under $2.
Prototypes are small, simple games. The main purpose is to find the "toy" as fast as possible. A good "toy" gives the game a solid foundation to put mechanics, iteration, and polish on top of. They also often serve as a practical way to learn something new.
Video games are like any other craft - you hone your skills by imitating the masters. Musicians start by playing The Beatles, and artists learn to paint like Van Gogh. Covers serve as an exercise to learn from best-in-class craftsmen.