The standard game mode (Bomb Scenario) involves either defending or exploiting a bomb site.
They have also a hostage mode and lots of other modes too. Almost every competitive match is played with the Bomb Scenario match type.
The game is simple but it’s very hard to become the best. It’s very competive game and the shooting mechanism makes it hard to hit players.
The game players can be quite toxic so some games can be terrible. But usually players are nice to you if you are nice to them. But the best scenario is to play with your friends.