The satellite revisit time is the time elapsed between observations of the same point on earth by a satellite.
It depends on the satellite's orbit, target location, and swath of the sensor.
"Revisit" is related to the same ground trace; a projection on to the earth of the satellite's orbit. Revisit requires a very close repeat of the Ground Trace. In the case of polar/hi inclination low earth orbiting reconnaissance satellites, the sensor payload must have the "variable swath" to look longitudinally (east-west, or sideways ) at a target, in addition to direct overflight observation, looking nadir.
In the case of the Israeli EROS earth observation satellite, the ground trace repeat is 15 days, but the actual revisit time is 3 days, because of the swath ability of the camera payload.