"Runtime" refers to the period during which a program or application is executing. It is the time when the code is actively running on a computer or device, allowing it to perform tasks and respond to user inputs. During this phase, the program utilizes system resources like memory and processing power to function effectively. In programming, understanding runtime is crucial for optimizing performance and debugging. Different programming languages, such as Python or Java, have their own runtime environments that manage how code is executed. These environments can affect how quickly a program runs and how it handles errors during execution.