Upon applying for U.S. trademark registration, there are many criteria your mark will have to meet before it is accepted by the examining attorney.

If it is determined that your mark merely describes a function or purpose of your services, your mark will be refused. 

For example, some marks that have been refused in the past are: 

SCREENWIPE held generic for an anti-static cloth used for cleaning computer and television screens

ATTIC generic for sprinklers installed primarily in attics

PERMA PRESS generic for soil and stain removers for use on permanent press products

WALLYBALL held descriptive of sports clothing and game equipment

BURGER held merely descriptive of cooking utensils

BREADSPRED held merely descriptive of jams and jellies.

The two major reasons for not protecting descriptive marks are:  (1) to prevent the owner of a mark from inhibiting competition in the sale of particular goods or services; and (2) to avoid the possibility of costly infringement suits brought by the registrant.  This thus enables businesses and competitors to have the freedom to use common descriptive language when merely describing their own goods or services to the public in advertising and marketing materials.