In bullet, most of a player's thinking has to happen before or between moves rather than during them — there simply isn't time for multi-move calculation on most moves. Strong bullet players rely heavily on automated pattern recognition, fast piece-moving technique (including efficient use of a mouse or premoves online), and opening lines played almost from memory.
Bullet has become extremely popular on platforms like Chess.com and Lichess, and top grandmasters regularly stream bullet games and compete in dedicated bullet events, sometimes reaching move rates of well over one move per second.
While entertaining and useful for sharpening reflexes and opening recall, bullet is generally considered a poor primary training format for improvement, since it does not exercise the deep calculation and careful evaluation that slower time controls require.