What is the technical name for this type of phrase in the English language?

You're right its a compound sentence! See look at the left side of the conjuction because. It says I got an F on the test and this is a sentence and can stand alone. Now look on the right hand side of the conjuction because. It says: I didnt study and its a sentence. Basically, a compound sentence is two senteces combined by a coordinating conjuction