Progress indicator is a visual indicator used to signify an ongoing operation that doesn't have a defined duration. Often circular and animated, Progress indicators communicate to the user that action is taking place, even if the completion time is uncertain. They're typically used in scenarios where data loading takes time, such as during content or page loading, form submission, or data processing tasks.

Progress indicator reduces user uncertainty during wait times, providing reassurance that the system is working as expected. This feedback loop is essential in maintaining user engagement and a smooth user experience, especially in latency-prone environments.