Explain why there are two high tides and two low tides?

There is one high tide on the side of the Earth facing the Moon and one on the opposite side, with low tides in between. This is because water on the side closer to the moon is pulled by the Moon's gravity, and the water on the opposite side is flung outward by centrifugal force. At the low tides (in between) centrifugal force and the Moon's gravity cancel out.