Yeoman is a title that is sometimes used in Star Fleet for an officer working as an administrative assistant.
Yeomen have clerical, administrative, and support duties in Star Fleet, mainly as part of the Support Division.
Officers, including Lieutenants and Ensigns can hold the position of yeoman, as well as enlisted personnel. Some yeomen assigned special duties held the title of "Captain's Yeoman."
In the 23rd Century, yeomen duties included acting as personal assistants, such as carrying a Starfleet tricorder and retrieving information for a starship's captain, preparing and delivering the captain's meals, or announcing one's arrival with a boatswain's whistle.
Most yeomen were enlisted personnel during their time in this position, with different grades of seniority, all the way down to "third class" as the most junior yeoman rank.
Yeomen assigned to larger ships or facilities, or to particularly distinguished captains, might have been junior commissioned officers preparing for the command track themselves.
By the 25th century, yeoman duties have mainly be consolidated to acting as the basic position of the Support Division, handling basic administrative tasks and cargo management.
A "Captain's Yeoman" has changed to become simply a personal assistant and liaison to a commanding officer.