What's the difference between an undercoat rake, a slicker brush, and a deshedder?

An undercoat rake has long, widely spaced metal teeth that reach down through the topcoat to pull loose undercoat without cutting. A slicker brush has dense fine wire pins for surface tangles, finishing, and removing already-loosened fur. A deshedder (FURminator-style) has a fine-toothed blade edge that grabs shedding undercoat very aggressively. Reddit groomers we read generally recommend a rake plus a slicker for double coats, and reserve true deshedders for short-coated heavy shedders.