Answer: A tidal force is related to gravity, but it isn't the same thing. It's really the difference between the the strength of gravity at two locations. The gravitational attraction between two objects (say the Earth and the Moon) decreases with distance.
The tidal force acting on an astronomical body, such as the Earth, is directly proportional to the diameter of that astronomical body and inversely proportional to the cube of the distance from another body producing a gravitational attraction, such as the Moon or the Sun.