Large tides are experienced when the Sun and the Moon are lined up with the Earth (new and full phases of the Moon). These are called Spring Tides (the name is not associated with the season of Spring). The amount of enhancement in Earth's tides is about the same whether the Sun and Moon are lined up on opposite sides of the Earth (full Lunar phase) or on the same side (new Lunar phase). When the Moon is at first quarter or last quarter phase (meaning that it is located at right angles to the Earth-Sun line), the Sun and Moon interfere with each other in producing tidal bulges and tides are generally weaker; these are called Neap tides.

Orbital Effects
As a consequence of tidal interactions with the Moon, Earth is slowly decreasing its rotational period. 10⁹ yrs ago, a day was just 18 hours long! Eventually the Earth and Moon will have the same rotational period and the Earth will always keep the same face turned toward the Moon. The Moon already keeps the same face turned toward the Earth, while it's orbit moves out 4cm each year.