Commas are used to separate words, phrases, and clauses to improve readability for the reader. They are used (1) before FANBOYS conjunctions; (2) after clauses beginning with "if" or "as"; (3) after time words, phrases, or connectives; (4) separating items in a series; (5) separating two or more adjectives modifying the same noun; and (6) before and/or after directly addressing someone. The document provides examples and exercises to practice proper comma usage.