What is the second stage of a rocket?

The second stage of a rocket is designed to operate after the first stage has completed its burn and separated from the rocket. It typically contains its own engines and fuel, which are used to propel the payload into its intended orbit or trajectory. This stage is crucial for achieving the necessary velocity and altitude for missions beyond Earth's atmosphere, including satellite deployment and crewed spaceflight. Once its mission is complete, the second stage may also detach or re-enter the atmosphere, depending on the mission's objectives.