We have three kinds of conjunctions: (1) coordinating, (2) correlative, and (3) subordinating. The coordinating and correlative conjunctions join elements in a series. When you join elements (two or more nouns, two or more verbs, two or more adjectives, and so on), you must make certain that each element appears in the same grammatical form and performs the same grammatical function. This is the rule of parallel construction.
The subordinating conjunctions introduce subordinate clauses.
We have seven coordinating conjunctions, which you can remember with the acronym BOYFANS (but, or, yet, for, and, nor, so). We have five pairs of correlative conjunctions (not … but, not only … but also, both … and, either … or, neither … nor).
We have scores of subordinating conjunctions, words like if, because, when, even though, although, though, as long as, as far as, and many others.