High tide is when the sea water reaches its greatest height within the tide cycle in its area. Low tide is when the sea water reaches its lowest height within the tide cycle. Normally there are two high tides and two low tides each day. This is the result of the relationship between the earth and the moon. The moon wants to pull itself closer to the earth. Water on the earth is the only thing that is not fixed so the moon is able to influence and effect water circulation in our oceans.