A social deduction game is a game in which a few selected players are chosen to trick the other players into thinking they are regular players like them. The few selected players, or imposters, will sabotage the other players efforts. The game ends when the imposters have stopped the regular players efforts or if the regular players have completed their objectives/found and eliminated the imposters.[1]
Examples include: Among Us, Blood on the Clocktower, Town Of Salem, One Night Ultimate Werewolf and Secret Hitler.
A popular game is "Who is the Spy?", which has gained a global popularity. The spy (imposter) and the regular players have undisclosed words. They cannot disclose the words, and if a regular player or the spy sees any strange things with a regular player, they could vote on whoever (except themselves) to find the spy. The spy's word is different from the regular players' words, and they can only describe it. This has led to a lot of cases where the spy wins because a regular player just didn't describe their word right.
Who is the Spy? is a different game from the examples above. Who is the Spy is played physically, although someone had ported a viral version onto an app before, which caused Who is the Spy to go world-famous.