What The Difference In Cigar Size, Shape, And Color?

I’d like to know what the difference in cigar shape, size and color? Examples: Why are some cigars longer then other and in doing so does it change the flavor? Why are some cigars almost black and others a fine tan does this make a huge difference? Also noticed there are many different shapes are these for show or do they have a purpose? Yeah i guess i have more then one question here. But i’d love all the help and anwsers i can get.