1. I went to the store, picked up some groceries, and then went home. In this sentence, the comma is used to separate the different actions (going to the store, picking up groceries, and going home) in a compound sentence.
2. The cat, who was sleeping on the couch, woke up suddenly. Here, the comma is used to set off a dependent clause (who was sleeping on the couch) from the main clause, providing additional information about the subject (the cat).
3. Jane is going to Hawaii, her dream vacation spot. In this sentence, the comma is used to set off a nonessential clause (her dream vacation spot) from the main clause, providing additional information about the noun (Hawaii) without changing the overall meaning of the sentence.