Copywriters prepare advertising copy for use in publications or for broadcasting and they write other materials to promote the sale of a good or service. They often must work with the client to produce advertising themes or slogans and may be involved in the marketing of the product or service.  Copywriters conduct research on their topics, which they gather through personal observation, library and Internet research, and interviews.

Copywriters must have exceptional written abilities, including command of language and grammar, and must be able to tailor their writing to the task at hand.  

Source: Bureau of Labor Statistics, Occupational Outlook Handbook