Commas are like the in-laws of punctuation. Nobody likes them, but they just show up uninvited anyway.
But seriously, commas are used to separate clauses, items, or to indicate pauses in sentences. Without them, sentences would be like awkward family reunions – everyone is just talking over each other and nobody is listening.
Commas are also used in computer programming, but that's a whole different story. Maybe we'll get to that on the Commas in Computers page.