1) The document discusses coordinating conjunctions and subordinating conjunctions. Coordinating conjunctions join grammatically equal or similar parts of a sentence, such as words or independent clauses. They include and, but, or, nor, for, yet, and so. Coordinating conjunctions always come between the elements they join.
2) Subordinating conjunctions introduce subordinate or dependent clauses. Common subordinating conjunctions include after, although, as, because, before, how, if, once, since, than, that, though, till, until, when, where, whether, and while. Subordinating conjunctions come at the beginning of the subordinate clause they introduce.