If you have ever seen the old cartoon "schoolhouse rocks" you know the function of a conjunction!  

Conjunctions join words or parts of sentences together.

There are four types of conjunctions

1. Coordinating (and, nor, but, for, yet, so, or)
2. Subordinating joins two clauses (subordinate to dependent) together)
3. Correlative (both/and; either/or; neither/nor; whether/or; just as/so; not only/but also)
4. Adverbial (join two equal clauses)