The mulching mower has a more powerful engine (always a 4-cycle on mowers made after 2004), a special blade and a special deck without an outlet for the clippings. The clippings are cut and recut, eventually falling to the lawn where they usually are not seen. Many mulching mowers are convertible for discharging or bagging by having a discharge port that can be opened or closed.
The non-mulching mower requires about half the power of the mulching mower and has a permanent discharge port, usually with provisions for bagging.
The advantages of the mulching mower are: faster mowing (without raking the clippings or repeatedly emptying the bag); no clippings deposited in the landfill; the clippings can reduce fertilizer requirement by 33%.