When I was first explained the copywrite on software it was easy (back in the '70-80)
It is like a book. You own it, can sell it or transfer to someone else (but can't keep a copy, like a real book), even borrow to another for a short time use. As it is a single copy used by only one person at a time. Simple. Now being able to store the game on a harddrive so you have the original copy and the playing copy. Does put a small wrinkle in the similarity as back in the day you ran a game from the disk/cartrage always.