Here's how to break it down:
* Independent Clause: A complete sentence with a subject and verb. It can stand alone.
* Conjunction: A word that joins two clauses together.
Example:
* "I went to the store, and I bought some milk."
* "I went to the store" is an independent clause.
* "I bought some milk" is an independent clause.
* "and" is the conjunction connecting the two clauses.
You DO NOT need a comma before a conjunction if:
* The two clauses are short and simple. For example: "I went to the store and bought milk."
* The second clause depends on the first clause. For example: "I went to the store because I needed milk."
Here are some more examples:
* Comma needed: "The dog barked loudly, but the cat ignored it."
* Comma not needed: "The dog barked and ran away."
* Comma not needed: "I went to the store because I needed milk."
Remember, the key is to look for two independent clauses connected by a conjunction. If you have that, use a comma!