The Moon is the main cause of ocean tides on Earth.
Its gravity pulls more strongly on the side of Earth facing it and less strongly on the far side, creating two broad tidal bulges. As Earth rotates through these bulges, most coastlines experience changing water levels, usually producing two high tides and two low tides during a lunar day.
The Sun also contributes substantially, but its tidal effect is weaker because it is much farther away. When the Sun, Moon, and Earth line up at new or full moon, their effects reinforce one another, producing spring tides. At quarter moons, they partly offset each other, producing smaller neap tides.
Actual tides do not simply mirror the Moon's position. Ocean-basin shape, coastline geometry, water depth, friction, Earth's rotation, and resonance can greatly alter their height and timing. This is why nearby locations may experience very different tidal ranges.