There is nothing important going on, except poking fun at some target. With one liners and humorous situations and maybe some slapstick, the bungling continuous uproariously to the end. The laughs often come from the special talents of character actors. Farce often contains the elements of neurotic reactions and insane situations. Situation comedy, on the other hand, takes a serious theme and portrays it in a humorous light.
Characterization is different for the two types of comedy.
In situation comedy, the central character drives the story forward and changes during the story. He will usually be a fairly normal person in situations that are close to reality, but treated with humor. He's a lovable guy who is easy to identify with, even if he has no past accomplishments. So we watch him stumble all over himself trying to learn social graces and win the lady. In another comedy, Chuck may be a bungling nitwit whom others use.