A coordinating conjunction, also called a coordinator, links parts of a sentence. This could be two independent (main) clauses, two noun phrases, adjectives, adverbials etc of equal importance.
They include: for, and, nor, but, or, yet and so,
There's a mnemonic for remembering them: FANBOYS.
It was cold. I wore a coat.
Both sentences are valid on their own, but they can be written so that they're obviously linked; "It was cold, so I wore a coat."
The three most used coordinating conjunctions are and, or, and but.
The coordinating conjunction and usually expresses addition or combination.
I attended the meeting. + My friend attended the meeting. = My friend and I attended the meeting.
The coordinating conjunction but expresses a contrast.
We were tired. + We were happy. = We were tired but happy.
The coordinating conjunction or expresses choice.
Would you like tea? + Would you like coffee? = Would you like tea or coffee?
There are two negative coordinating conjunctions: neither and nor.
She spoke neither German nor French. (Here, "nor" is part of the "neither ... nor" construction).
!Note - nor, for, and so can only join independent clauses.