Here are three ways to explain the CC RULE:
CC RULE: When a conjunction connects two independent clauses, you must use a comma before the conjunction. An "independent clause" is part of a sentence that could be a sentence by itself. An independent clause is a complete thought with subject and predicate.
EXAMPLE:
We should travel to Italy in September, and take a train to Paris in October.
CC RULE: When a conjunction joins two independent clauses, you should use a comma with it. The proper place for the comma is before the conjunction.
EXAMPLE: Independently owned toy shops are my favorite stores, but they not easy to find these days.
CC RULE: When you have two independent clauses connected by a conjunction
-----> You need a comma.
During recess we played with our friends, but we never thought about the kids who had no friends.
