Time dilation is the difference in elapsed time when measured by two clocks, either because of a relative velocity between them, or a difference in gravitational potential between their locations. When time dilation isn't specified it usually goes back to the effect due to velocity. Time dilation is most known from the movie Interstellar because of a black hole but you don't need a black hole for it to be present you need something to go fast or around 1/10 the speed of light. At that threshold, the difference between you and a stationary object's relative time would matter meaning you would be aging slower than said object.