Combos are ready to use, "out of the box". All you have to do is wind line onto the spool and add the terminal tackle of your choice. Some combos even come with line pre-wound. In general, combos are attractively priced, which makes them appealing for budget and value-conscious customers. A combo has a matched rod and reel, so you don't have to worry about the action of the rod (and whether it has the right flexibility) or the gear ratio of the reel (and whether it has enough mechanical advantage). A fishing tackle expert has done this work for you, so you don't have to.
What Rod and Reel Combos Are
A combo is a matched rod and a reel set, configured for a specific type of fishing.