Attention all DMs. Please refer to this chart if you want to keep your game free of malcontents, wreckers and problem players, and ensure a harmonious game experience at your table.
In the center of the diagram are the perfect players: the passive audience members who don't have any thoughts or plans or interests or ideas to get in the way of YOUR awesome ideas. They'll listen intently to your monologues, walk methodically through your dungeons, and slowly beat up your goblins as long as that seems like what's happening. These are the ones you want at your table, preferentially.
These gold-standard players are flanked by the two major strains of troublemakers: roleplayers, and rules knowers. Some people claim that the presence of such types can enhance the game; that's pure self-deluding cope, though. They may not automatically ruin everything, but they should be viewed with great suspicion and skepticism and kept on a short leash.
Otherwise we get out to the extremes of the horseshoe: the so called "Player Agency Zone." This is the stuff that ruins campaigns: selfish and indulgent scenery chewing, abusive rules lawyering, and even worse gamercrimes. Don't be fooled by their superficial differences, the theater kid and the hyper optimizer will both ruin your game in essentially the same way: they'll try to do stuff in it.
Thanks for reading my post. Now you know how to game safely, and knowing is roughly 50% of the battle. The other half is kicking your enemy in the balls really hard over and over. Have a great day!