In the U. S. Navy, this is a rating, or occupational specialty, responsible for administrative tasks such as typing, filing, processing documents and forms, keeping manuals up to date, and especially, serving as clerks to the commanding officer.
After the rank of E5, or Petty Officer Second Class, a yeoman may attempt to become a Legalman, the Navy's paralegals. A yeoman may also specialize in serving the administrative needs of admirals (much more emphasis on protocol and etiquitte here). These yeoman are called flag writers.