Respawning is where a player loses all of their health in some game modes if a player is fallen a timer will pop up for neither 20 or 30 seconds during this time the player cant respawn till the time stops. Mobs Respawn regularly without any time penalty (except for day unless its on Normal or Hard) Special mobs like the Dragons and demons take longer to spawn (Aliens are not affected by this since they only spawn near space goo).