I can clarify this topic as little more,
A grinding wheel is designed to cut steel. The wheel is made up of the grit, and the bonding agent. Different wheels are designed to cut different types of steel. Soft steel and hard steel. Generally the harder the steel, the softer the wheel, and the softer the steel, the harder the wheel, works best.
As the wheel turns at a high rpm, it contacts the steel under a high pressure. Each single grit in the wheel is sharp, and it removes a tiny amount of steel with each grit.
As the grit gets dull from cutting the steel, the pressure increases between the wheel and the steel, and the dull grit is released from the wheel, because the bond is weaker then the pressure applied, and it breaks free.
So the wheel is self sharpening, if the correct wheel is being used for the application.
Grinding wheels are designated by the size of the grit by a number, say, 46 grit, 60 grit, 120 grit. The higher the number the smaller the grit size.
A letter is designated for the hardness or softness of the bonding agent. the letters run from A to Z
So there are many types of wheels to choose from for the many different types of metal to be ground. Also a coarse grit wheel will act softer then a fine grit wheel, so experience and how the wheel is used help a lot in correct grinding.
This refers mostly to surface grinding in a machine shop, but the correct wheels on a pedestal grinder also is important.
In the Navy Machine shop, we were taught to identify types of steel by using a pedestal grinder. The color of the spark. and the length of the spark is different for different steels. For example, high carbon steel has an orange spark that long with many sparkles per inch. If you watch paper burn, which is high in carbon the flame is bright orange, as is the carbon in high carbon tool steel.
Cold rolled steel has a whiter spark and less sparkles on the grinding wheel.
Ypu can lose the temper in steel by grinding incorrectly. If you use a 46 grit wheel that is fairly soft, say no higher the G in bond hardness, and hold the plane iron or chisel, so that the wheel is spinning toward the handle end of the chisel, or the end opposite the cutting edge of the plane iron, the heat will be directed away from the tip of the tool.
Light pressure should be used and moving the tool across the wheel at all times will produce a burn free grind. Correct grinding is a slow process.
Dressing the wheel frequently and quenching the tool in water helps a lot. Because you are not using the high pressures used on a surface grinder then the wheel can get dull more frequently, thus wheel dressing helps.
Slow RPM grinders help those not familiar with grinding wheel choice, and proper grinding technique. A 3600 rpm grinder can grind tools all day long, without softening the tool, but a 1750 rpm wheel can be used, with a finer grit wheel.
The first thing to do to a chisel or plane iron if it is chipped, or very dull, is to grind a flat perpendicular to the point of the tool sharp edge, of about 1/32" to 1/16", preferably with a 60 grit wheel or higher. Very lightly as not to distemper it.
Then proceed to remove the material across the intended angle of the tool as explained above.
The tool should never get too hot to be held in the hand at the point of the grind. About 120 degrees is very hot to the hand.
I hope this was helpful in explaining the answer to your question.