Abrasive wheels are special disks (cylinders).
The cylinder is rotated at a very high speed and they are commonly used for the sharpening of objects.
Abrasive wheels in the olden days never relied on electricity to power them like today.
They were in fact run by the user working a pedal with their foot or sometimes a crank was used which was operated by hand.
When the electric motor was introduced, this was the end to manual powering of the wheels.
However, they had to be designed slightly different and had to be manufactured to greater radial stress.
If they were manufactured the same as the manual powered wheels, they would fly apart as the cylinder was spinning.
In some cases the structures were actually given extra support and reinforced by use of impregnated fibers.
These often required the use of a lubricant or a coolant, because of the speed the abrasive spins at and the contact it makes with the workpiece, a lot of heat is produced and in turn this can severely damage the workpiece, depending on its material.
The coolants main purpose was to reduce frictional heat build up and protect the workpiece.
The lubricant was often kept in a shallow half circle bowl, so when they spin the lower half of the it passes through the liquid / coolant in turn preventing the workpiece from sustaining damage.
Diamond wheels are also another type.
In summary it is a disk that has been impregnated with an abrasive and spun at high speed for sanding and grinding etc.