A cooperative game is a game where multiple players are all working together to achieve the common end of the game. This isn’t the same thing as a game where players can cooperate (like many trading games or war games), but games where the entire point of the game is for two or more players to work together to win it.
Cooperative game designs are great for making games for players who aren’t interested in direct conflict.
They’re also good for making somewhat basic problems much more complicated and engaging. It’s one thing to just lift a box, but if one player has to lift the box, and another player push it forwards, you’re going to make something that wasn’t quite a challenge into a problem of communication.
Honestly, though, cooperative games are excellent for people who just don’t want their games to be about butting heads and would rather work together.
One of the big problems that cooperative games tend to get is commonly called quarterbacking. The idea is that as long as all players are collaborating on the project of the game means that it’s possible that one player can take control of the play – that there is, in any situation an optimal play, and then it falls to one player to make that play as best they can.
This can mean that in any given play situation, one player might not be making many choices, and one player might be making more. There are ways around this, but quarterbacking is the biggest problem with pure cooperative games.
Pandemic, and most of its connected works. Mysterium. Hanabi. Spirit Island.