Time dilation, as described by the theory of special relativity, refers to the "slowing down" of a clock for an observer who is in motion relative to that clock. This means that observers moving at different velocities will experience time differently.
In physics, time is not absolute but is relative to the observer’s motion. Each observer determines that clocks in motion relative to them run slower. This effect is typically negligible in everyday life but has significant implications in areas such as the global positioning system (GPS), where relativistic corrections are needed for accurate positioning due to the satellites’ motion and Earth’s gravitational field. Time dilation has been confirmed through observations of particle lifetimes at high speeds and experiments involving atomic clocks in airplanes.