Here's why:
* Subordinating conjunctions join a dependent clause to an independent clause. A dependent clause cannot stand alone as a sentence, while an independent clause can.
* Coordinating conjunctions join two independent clauses.
Examples:
* Subordinating conjunction: "Because it was raining, we stayed inside." (The dependent clause is "Because it was raining.")
* Coordinating conjunction: "We stayed inside, and we watched a movie." (Both clauses are independent.)