The bridge is the main command center of a starship, where the captain and senior officers control navigation, tactical systems, communications and science functions.
On most Starfleet designs the bridge sits at the top of the primary hull, with the captain's chair facing a large main viewscreen and stations arranged for helm, operations, tactical, science and engineering. Crews reach it by turbolift, and from it the captain directs every major decision aboard.
Bridge design changed over time, from the compact layout of the original Enterprise to the larger family-friendly bridge of the Enterprise-D and the cramped, combat-focused bridge of the Defiant.