The moon is important for many reasons. One being tides, it controls the ideas like high tide and low tide. It has phases, eight of them.it has eclipses like a lunar ad solar. I will explain these now.
Phases like these allows people to tell the time through the moon. They have these because of it reflecting the suns light. When the view is changed on the moon it looks like it has phases. This is not the earth eclipsing the moon. This does happen but that is to do with something else.
Tides are caused by the moon. As it orbits earth it attracts the water. The water then tryst to go towards it or it stays on the other side. This also causes a small layer in between them. That's why there are two high tides and low tides.
There are also two types of high and low tide. A neap tide which is smaller because it is the moon fighting the sun. A spring tide happens when the sun and the moon combine there gravity. Neap tides happen when the moon the sun and earth make a right angle. A spring tide happens when they line up in a straight line.
The moon can cause eclipses or be eclipsed itself. These are called solar and lunar eclipses. In the event of a solar eclipse the sun is covered by the moon. In the event of a lunar eclipse the moon is covered by the earth. There can be partial lunar eclipses and complete lunar eclipses depending on position.
Without the moon earth would be different. There would be no tides. Eclipses would not happen that allow scientists to study the sun. People in third world country's would not have a way of telling time. there would be eve less light at night. With out the moon it would be horrible.