Crampons are as varied as ice axes, and like ice axes, so are the uses they designed for. There are crampons designed for steep ice, for more alround climbing and mountaineering, for hill walking and for purely walking along pavements. And you cannot fit any crampon to any boot.
Steep Ice/Mixed Crampons: Crampons designed primarily for steep water ice - though there are some crossover models. These should only be fitted to very stiff (B3) boots.
Mountaineering Crampons: Crampons designed for everything from hillwalking to alpine climbing to Grade V Scottish ice and mixed. Can be fitted to medium stifff B2 or B3 boots.
Walking Crampons: Crampons designed purely for winter hill walking. Can be fitted to most boots (dependant on binding) though the recommendation is some stiffness (B1) or above.
Ultralight Crampons: Alloy crampons which are only suitable for occasional use on pure ice and snow.
Spikes: Spiked devices for use on icy flattish ground.