Depends on the context. Rocktron units may use them interchangeably. A patch change generally means changing a particular 'voice'. ie., patches on a Replifex - each patch could be considered a unique voice - chorus/delay/pitch on one patch, the next patch might have reverb only. Can you tell me which pages you're looking at, I've had extensive hands-on with the Rocktron stuff - including the All Access. If I read what you're looking at I can surely help you figure it all out, and explain it better.