https://en.m.wikipedia.org/wiki/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.
For those who can’t be bothered to watch the video: Biden talks with Trump supporter, signs a presidential hat, trades for the Trump supporter’s hat, briefly wears it.
Also jokes about being so old he forgot his name, tells the guy “hell no” when asked if he wants him to sign the Trump hat, and tells people not to eat dogs.