Gravitational time dilation is a phenomenon predicted by Albert Einstein's theory of general relativity. It states that time passes more slowly in stronger gravitational fields. For example, a clock located near a massive object, like a planet or a black hole, will tick more slowly compared to a clock that is farther away from such a mass. This effect has been confirmed through various experiments, such as comparing atomic clocks at different altitudes. The clock on the ground, closer to the Earth's gravity, runs slightly slower than the clock on a high mountain. This illustrates how gravity can influence the passage of time.