A complex sentence is made up of one independent clause and at least one dependent clause.

A compound sentence consists of two or more independent clauses joined by a coordinating conjunction (for, and, nor, but, or, yet, so).

An independent clause is a group of words that can stand alone as a sentence; it has a subject and a verb.

A dependent clause is a group of words that cannot stand alone as a sentence; it depends on an independent clause to provide meaning.

A semicolon is used to connect closely related independent clauses or to separate items in a complex list.

An appositive is a noun or noun phrase that renames or provides additional information about another noun.

You need two commas to set off an appositive that is in the middle of a sentence.