When to use:
A Compound Sentence is a sentence with more than one subject or predicate. A predicate can be a noun or a verb.
Here, a comma is used to separate or divide two or more clauses in a compound sentence. This sentence is split up by a conjunction (a connecting word). The comma is placed at the end of the first clause (before the conjunction).
Incorrect: She was late and she was very angry.
Correct: She was late, and she was very angry.