Final answer:
Commas are used to separate elements in a series or list, and to join independent clauses. They are also used with dependent clauses that come before independent clauses.
Step-by-step explanation:
Commas are used to separate elements in a series or list. For example, 'I bought apples, oranges, and bananas at the store.' The use of a comma before the conjunction 'and' helps create parallel structure.
Commas are also used to separate independent clauses when they are joined by a coordinating conjunction, such as 'and', 'but', or 'so'. For instance, 'I went for a walk, and I saw a beautiful sunset.'
When using dependent clauses, a comma is placed at the end of the dependent clause if it comes before the independent clause. For example, 'Because it was raining, I stayed indoors.'