What is meant by the term mulching or mulch mowing?

At Fair Dinkum Lawn and Garden Care we use specially designed Honda lawn mowers. These machines have a high powered 4 blade cutting system which chops the clippings up much finer than a regular twin blade system. When set in mulching mode the clippings are returned to the lawn as mulch. On a well maintained lawn it is not easy to tell that the clippings have actually been returned to the lawn. In fact, it is quite common for a lawn to look much greener after mulching as opposed to catching.