This concept can get complicated, so I’ll break this down to the simplest form (as seen on the SAT).
We need to start with two complete sentences, also known as independent clauses:
How can we fix the comma splice? That’s where the FANBOYS come in:
The technical name for the “FANBOYS” is coordinating conjunction, but don’t worry about that: the SAT doesn’t test you on the name. What actually matters is the role that the coordinating conjunctions play:
The sentence is now correct. On the SAT, the most common run-on sentence error is the comma splice. Placing one of the FANBOYS between the two independent clauses (i.e. complete sentences) solves this problem.
Remember to embrace the FANBOYS: they can help you earn easy points on the SAT.