Tides are formed by a combination of gravitational attraction from the moon and the sun, as well as the centrifugal force generated by the rotation of the Earth. The position of both celestial bodies affects the surface height of the tides as water is gravitationally pulled upwards relative to their positions.
Although the moon is smaller than the sun, its nearness to Earth means its gravity has twice the effect on tides. Portions of the ocean are pulled together, creating high water regions when the moon and sun exerts its effects. Due to the constant mass of the oceans on Earth, this effect creates areas where the water levels become much lower.
The movement of tides and the oceans' surface largely follows the orbital plane of the moon. The moon's orbit is oriented at a 23-degree angle relative to the Earth's equatorial plane. This causes the water levels at the equatorial regions to fluctuate at a smaller range compared to other parts of the Earth.
While gravitational pull from the moon and sun accounts for a large portion of tides, some are caused by atmospheric pressure variances. Some large tidal movements can also be caused by underwater earthquakes or volcanic eruptions.