The captain oversees the status of the ship and gives orders to each of their officers. He or she is also able to take over each role position to perform actions personally.
The engineer controls the energy flow of the ship. They can direct energy to specific systems and manage repairs of the ship.
The helm controls the ship itself. They fly the ship and are also responsible for Impulse and Warp travels.
The tactical officer is responsible for weapons, shields and targeting. They fire the ship's weapons (Phasers or Photon Torpedos) at enemies and raise or lower the shields.
A few systems are shared between the Engineer, Helm and Tactical: the Teleporter and the System Disruption. All Stations are able to control these systems but only one station at a time can open the panel.