Drumlins are elongated hills of glacial till (unsorted sediment deposited by glaciers) that are typically oval-shaped in plan view and have a steeper, spoon-shaped "stoss" side facing the direction of the glacier's advance and a gentler, more elongated "lee" side facing the direction the glacier retreated.

Here are some key characteristics of drumlins:

* Formation: Formed by the erosive and depositional activity of glaciers. The glacier sculpts the till as it moves over it, creating the distinctive spoon-shaped form.

* Orientation: Usually aligned parallel to the direction of glacial flow.

* Size: Can vary in size, ranging from a few meters to several hundred meters long.

* Occurrence: Found in areas that were once covered by glaciers, particularly in the Northern Hemisphere.

They can be found in groups, or "drumlin fields," which provide valuable information about the direction and movement of past glaciers.