Crampons, which look like metal skeletons with sharp points, attach to your climbing shoes for extra traction when you're climbing on snow and ice. Usually made of steel or aluminum, the frame fits beneath the soles of your shoes and is attached by adjustable straps or clamps.
Most crampons have 10 or 12 points. If they have 12 points, the two pointed straight out on the toe make frontpointing easier. The sharp points bite into the ice or whatever surface you're climbing for a more secure hold.
Crampons are specialized for various activities. For everyday winter walking over snow, super-lightweight traction devices are a good choice. Other models are suited for snow and glaciers, technical hiking and winter or summer mountaineering. You can even find crampons designed especially for frozen waterfalls or routes that involve both ice and rock that allow you to adjust the length and the pitch, or angle, of the points.
Most crampons feature a semi-rigid design that performs well in a variety of conditions from simply walking over winter snow to moderate ice climbing. Some allow you to adjust the linking bar between the toe and heelpiece (which helps gives you traction and support when walking in the snow and ice) to change to a flexible mode for more comfortable hiking over forgiving terrain.