The spacecraft structure adopts the principle of cabin layout, and all components of each subsystem are placed in a compact cabin, which is convenient for inspection and assembly and replacement in case of failure.
Gemini spacecraft consists of service section and reentry section, in which the service section consists of propulsion module (instrument module) and orbital module.
The reentry part is the familiar return capsule.
So Gemini spacecraft consists of two parts: service module and re-entry module.