You can cut slots on the table saw, but doing them on the router table with a slot cutter has some definite advantages. For one thing, you’ll get perfect flat-bottomed cuts, something not all saw blades can do. And, because they cut horizontally, creating slots in the edges of extremely wide stock is far easier and safer than attempting to balance the same workpiece vertically against the fence on your table saw.
You can also buy slot cutters in a variety of thicknesses — usually 1/16″ to 1/4″ — and in versions with and without guide bearings. As with rabbeting bits, some slot cutters come with a set of different-sized bearings to adjust the slot depth. Slot cutters typically come with either three or four cutting edges or “wings.” However, some newer slot cutters use a pair of two-wing cutters that stack atop one another on the shank, using thin shims to adjust slot width the way a set of dado blades does.