When you have two complete sentences — also called independent clauses — and you connect them with a conjunction (and, but, or, for, nor, yet, so, for example), you need to insert a comma before the conjunction.
But if the second clause that makes up the sentence is a dependent clause (lacks a subject), no comma is necessary.
These are complete sentences / independent clauses that can stand alone. Each has a subject and verb: ContinueLike it? Share it!