Tides are the rising and falling of the ocean shore. What are tides caused by?

Tides are the rise and fall of the oceans. They are caused by the gravity, or pull, of the Moon and Sun. The Moon's gravity is the main force in causing tides. It makes the oceans bulge out toward it. Another bulge occurs on the opposite side, because Earth is being pulled toward the Moon and away from the water. The water on the side farthest away from the Moon is least affected by its gravity.

Tides are caused by gravity of the moon and sun