One website I know is
this but it's only for dota 2.
Think of it like poker, there is a tourny owner that makes this possible, every contestant puts up a certain amount, whoever still stands at the end of the game gets the money and tourny owner just takes out their share (rake) from it. Sounds pretty amazing if you ask me, definitely would worth a try and could become big.
There was a thread started here years ago the user's plan was to create a little tournament and each user pays for an entrance fee for the prize pool. I only remember it because they had a free slot for the first user to join.
If you are interested in esports such as Counter-Strike or Dota
OP is not looking for a sportsbook. He wants to join a small esport tournament.
Op its best you elaborate your post and make it clear for you to get any tangible answers to your question
Because it confusing to say the least
It's not confusing if you know most of the games offered by casinos.