A moraine is a deposit of glacial till -- rocks, gravel, and dirt that were once carried along by the glacier.

A glacier is basically a river of ice, and like any river, glaciers too have their ends. In the case of a glacier, the end is not necessarily the ocean; a glacier ends when its flow enters a warmer area and melts. This point is called the end or foot of the glacier, and is usually the primary ablation zone. Obviously, when a glacier melts, it leaves behind whatever debris it was carrying along with it. It also leaves behind water, which may carry away some of the lighter debris, but ice can carry a much heavier load than can water. That which is left behind is called an end moraine or a terminal moraine.

Over hundreds of years, the glacier slowly builds a large pile of till, which may be kilometers wide and deep, and up to about 100 meters tall -- there is wide variation, and the largest moraines have been eroded since they saw their peak in one of the Earth's many ice ages. They are usually low, elongated hills made of unstratified rubble. They last a long time, and you may very well have moraines in your area; your area may even be an end moraine: Long Island is a moraine; Vaughan, Richmond Hill and Aurora in Ontario, Canada are built on the Oak Ridges Moraine; and unsurprisingly, the city of Moraine, Ohio is also built on an end moraine.

While a glacier may continue to flow for centuries, the location of the foot may advance and recede over that time. If the glacier advances, it may push the end moraine ahead of it, smearing it out and pushing it to the new foot; these are called push moraines. (this may also be how drumlins are formed). If a glacier retreats it will leave the end moraine behind it, leaving smaller deposits (dump moraines) until it reaches a point where it stops retreating, forming a new stable foot. The end moraine often helps contain a glacial meltwater lake.

If you liked the end moraine, you may also like the lateral moraine, the medial moraine, and the ground moraine (AKA glacial drift).