The three overlap but are not the same, and viewers usually know exactly which one they want.
Mud
Wet soil, puddles and mud pits – the cleanest of the three, often with wrestling, boots or full-body scenes.
Manure
Cow dung and manure from the farm: heavier, smellier and tied to the farm setting. Most clips in the rows on this site are manure clips.
Scat
Human scat is a separate niche. Some farm creators do both, but the tags tell you which is which before you buy.
Related: filming on a farm.