Service modules are specialized components in various systems that provide essential functions or services. They are designed to be modular, meaning they can be added, removed, or replaced without affecting the overall system. This flexibility allows for easier maintenance and upgrades, making them valuable in fields like software development, aerospace, and manufacturing. In the context of space exploration, a service module often refers to a part of a spacecraft that supplies power, propulsion, and life support. For example, the Apollo spacecraft included a service module that housed critical systems needed for the mission, ensuring the crew's safety and the spacecraft's functionality during flight.