What task does a cotton gin do to make the crop ready to sell ?

The task that a cotton gin does do to help make the crop ready to sell is that it separates the cotton seeds from the cotton.

A cotton gin was another gift of the industrial revolution to the society. Eli Whitney invented a machine that could speedily bifurcate cotton seeds from the cotton. This allowed the farmers to quickly turn the cotton fetched out of the farms into readily ready to sell cotton.

This is considered one of the reason for the growth of slavery in America which lead to the American Civil War.