A combo edge, also called a partially serrated edge, puts serrations on the rear portion of the blade nearest the handle and a plain edge on the forward portion. The idea is one blade that can both saw rope and slice cleanly.
The heel of the blade is where you have the most leverage and the most control for a hard pull, which is what sawing rope needs. The forward section and the tip, where fine work happens, are left plain.
Typical splits run about a third serrated to two thirds plain, though it varies by maker.
A combo edge does both jobs adequately and neither perfectly. You get a shorter plain edge for slicing and a short serrated section for rope, and long draw cuts hit the transition point awkwardly.
Most experienced users end up preferring a full plain edge plus a dedicated serrated blade if they need both. Combo edges make most sense when you can only carry one knife.
The term is not academic here. 66 of the products currently on our shelves describe this feature in their own manufacturer specifications, across 7 of the nine brands we stock. Examples in stock right now include Case Steak Knife Set Walnut, Gerber Propel Downrange A/O, Gerber Center Drive Rescue Berry.
Everything below is pulled live from the catalog, so what you see is what is actually in the Woodlawn warehouse today.