Enjoy the beer that you deserve.
Cohumulone is one of the compounds found in hops known as the alpha acids. It is a part of the soft resin from the hopís lupulin glands. It is these compounds that are largely responsible for providing the bitterness to hopped beer.
The amount of cohumulone present is considered by some to indicate the degree of harsh bitterness the hop will have. Noble hops contain very small amounts of this compound.
The amount present in a given hop is expressed as a percent of the total alpha acids in that hop.