Unfortunately a fad that's been around since 2016/2017 or so. The largest one is probably Fortnite BR, they tend to have a few million monthly active users.. although whenever there's an event there's a lot more who just log in for the event. Typically a BR is one person (or one duo or one squad, etc) vs everyone else. No one respawns, except for specific exceptions, and the last person/squad/whatever standing wins. There's an official team deathmatch type mode as well but the children tend to scoff at it as if it's just training wheels for "the real mode" instead of realizing that it's more fun to have respawn than to not have it.
Generally a mass player "there can only be one" fight to the death last player standing wins game.
As opposed to, say, team orientated Capture the Flag scenario's.