For many people, one of the most confusing aspects of English grammar is the semicolon - when should it be used? Can I use a comma instead? In fact, the semicolon is often seen where a comma should be, thus breaking up a sentence that shouldn't be.
The following image should help clarify when to use a semicolon:
So, if a clause is dependent, meaning it could not be a complete sentence on its own, then a comma should be used. If a clause is independent, a semicolon should be used.