Most ceramics cannot be machined by traditional metallic tools due to their high brittleness and hardness. Instead, we use diamond grinding tools to machine them.
Imagine that we hammer on a concrete wall to make a hole. That is exactly how machining ceramics with a diamond grinding tool is like. Each diamond grain fixed on a tool works as a hammer. So basically, it is like breaking the ceramic wall with a countless number of hammers.
Hammers in general come in a variety of different sizes and shapes. When strength is needed, a larger hammer with flat hammer head is used. If precision is needed, a smaller hammer with sharp edge is used.
The same applies to a diamond grinding tool. Diamond grains also vary in sizes (so-called grit) and shapes. The larger the grit, the smaller the grain size. The smaller the grit, the coarser the grains are. As for the shapes, the grains with sharp edges have shorter life but can remove surface material on impact, whereas those with blunt edges have less wear and longer life. For better efficiency in rough machining, we use a diamond grinding tool with coarser grains which can last longer. However, for precision machining, we choose the one with sharp-edged smaller grains.
Also, hammers come in a variety of materials such as iron, copper, and plastic. Similarly, in diamond grinding tools, there are different kinds of bonds, such as electroplate, metal, resin, and vitrified, are used to fix diamond grains on a tool.