What happens when you buy a game digitally?

When you buy a game digitally, what exactly takes place behind the scenes? Do you instantly gain access to the full game, or is there a download process involved? How does the payment process work, and are there any potential security risks to consider? Can you play the game offline after purchase, or is an internet connection required at all times? Additionally, how does digital ownership differ from traditional physical copies of games, and what are the implications of this shift in the gaming industry?