en.m.wikipedia.org/…/Sweetening_(show_business) gives a quick rundown.

In television, sweetening refers to the use of a laugh track in addition to a live studio audience. The laugh track is used to “enhance” the laughter for television audiences, sometimes in cases where a joke or scene intended to be funny does not draw the expected response, and sometimes to avoid awkward sound edits when a scene is shortened or more than one take is used in editing.