From the Super Mario Wiki
Snufits are floating, Boo-like enemies similar to Snifits. They first appear in Hazy Maze Cave, specifically in the Metal Cavern, during the events of Super Mario 64 and Super Mario 64 DS. In Super Mario 64, they are only floating miniature Snifits, but one unique trait is that Snufits inflate like a balloon before firing. When Mario comes too close to one, it will shoot balls out of its mouth in short bursts. Snufits can be defeated by jumping on them. However, in Super Mario 64 DS, they appear to be normal sized ghost Snifits.
They later make an appearance in Mario Party 2 on the Space Land board as the Snufit Police, but they are referred to as Snifits in some copies of the game. They can fire small projectiles similar to rocks.
Although their English name in Super Mario 64 is similar to but different from that of Snifits, their Japanese name is identical, implying that they are intended to be the same. Some versions of the English release of Mario Party 2 (including the Virtual Console release) also refer to them as Snifits in addition to other versions which use the name "Snufit".