The CS:GO Raffle still exists, but more gamblers are playing Case Openings
The Raffle game type is a simple lottery where there are a prize or prizes. You then buy a raffle ticket that gives you a chance to claim one of the prizes. When the raffle starts one or more numbers will be drawn and announced, answering the question if you won or not. You just have to hope that you have been lucky enough for them to announce the number on your raffle ticket!
This is an old game type and was popular for a while for CS:GO skins. CS:GO Bounty still have this game type but otherwise there isn’t that many providers. The case opening services largely replaced the old raffles.
With that said the raffle system is used for some other skin gambling games.