How does the moon cause high and low tides?

The moon exercises a force of attraction on the Earth. This pulls at the water in the oceans lying on the side of the Earth that faces the moon. This often gives rise to 'water mountains', which generally occur near the coasts and are known as 'high tides'. On the side of the Earth that lies opposite to the moon, low tides are found near the shores. Since the Earth keeps rotating on its axis, it moves below the waves and every 12 hours 'comes past a low tide'. As a result, there is a high tide every 12 hours. At new moon, when the sun and the moon are present on the same side of the Earth and both pull at the water on the Earth, the tide is especially high and is known as 'spring tide'.