Conjunctions are words that join together other words, phrases (groups of words), or clauses (groups of words with a subject and verb).
Co-ordinate conjunctions join words, phrases, or clauses of equal rank. There are two kinds: simple and correlative. The simple co-ordinate conjunctions are the following: and, but, or, nor, for, and yet. (For and yet can only join clauses.) Correlative conjunctions are always in pairs. They are either-or, neither-nor, both-and, not only-but also, and whether-or.
Subordinate conjunctions join dependent clauses to independent clauses. I will refer to them simply as co-ordinate, correlative, and subordinate. Some common subordinate conjunctions are after, although, as, as if, because, before, if, since, so that, than, unless, until, when, where, while.
The co-ordinate and correlative conjunctions should be memorized since they are common and few in number.