A steward or chief steward was an enlisted crew member serving aboard a ship as an attendant, managing food services in various capacities, including food server and assistant chef.
In the early 2150s the Enterprise (NX-01) had several stewards aboard who assisted the ship's chef, including Crewman Daniels. (ENT episode: "Cold Front")
A chief steward also served aboard the USS Enterprise in the mid-2260s, and was in charge of monitoring food supplies. When food supplies became shockingly low in 2267, the steward informed Doctor Leonard McCoy, who brought his concerns to Captain James T. Kirk. (TOS novel: Mission to Horatius)
Prior to the 2370s, Richard Bashir worked as a third-class steward on a shuttle run. (DS9 episode: "Doctor Bashir, I Presume")