Fair can be used as a noun, adverb or an adjective.
Fair as a noun- is an exhibition of something
Fair as an adverb – means in a legal manner, without tricks or cheating
Fair as an adjective – means pleasing appearance, just and unbiased, light tone complexion.
Fair Examples
It looks like it will be fair weather today (adjective)
We had a ferris wheel ride and ate candies in the funfair. (Noun)
The team won the football game but did not play fair. (adverb)