Anna ♥'s List: Starfleet positions, ranks, duties and responsibilities

The helmsman (or helm officer) was the Starfleet crewperson who operated the helm console on 23rd century Federation starships.
The helmsman of those vessels worked in concert with the navigator, who plotted the ship's course. On the USS Enterprise, the helmsman controlled both the speed and attitude of the ship, as well as the ship's weapon and shield systems.

"Helm (or helm control) is a term for the flight control operations onboard a starship or shuttle. Helm is responsible for controlling the flight operations of a ship, including warp, impulse and thruster control. Helm is also responsible for controlling the ship during a landing sequence or docking procedure.
The term is derived from old Earth navy parlance. In the 23rd century, in Starfleet, the helm was usually manned by a helmsman. The term fell into disuse in the 24th century, and while "helm" is still generally used to refer to flight control operations, the position manning it is called the flight controller, or conn (the latter of which is also used to refer to the station itself).
The actual helm console is usually near the front of a Starfleet ship's bridge. On some vessels, the helm stands alone (USS Voyager, USS Defiant, NX-01 Enterprise). Traditionally, Starfleet vessels have two forward positions, so the helm is paired with another station. The other console was the navigator on 23rd century ships such as USS Enterprise. Other consoles paired with the helm have been the stations of the operations (USS Enterprise-D) or tactical (USS Enterprise-A, USS Enterprise-C) officer. "

In Starfleet, the navigator held the position responsible for projecting the course of a starship and for determining a ship's position, velocity, and direction in relationship to a course. The navigator could also use the ship's navigational sensors to determine the positions, speeds, and trajectories of other objects.

"The navigation console was a console located on the bridge of a starship. The console was designed to monitor and project a vessel's course and velocity. The console also included sensors to determine the position, speed, and trajectory of other objects and ships.
In the 2250s and 2260s, the navigation console was separate from the helm. In addition to coordinating course changes, the navigation console was also designed to allow crewmen to manage weapons firing. (TOS: "The Corbomite Maneuver", "Obsession") By 2266, this function of the navigational console was taken over by the helm. (TOS: "Balance of Terror")