Carbide, in construction and industrially, is an EXTREMELY hard material often used on the tips (or as a solid piece) for router bits, saw blades, planer blades, masonry bits, and certain grinding pads.

Carbide is used very commonly for wood working and a lot of metal working. Accurately it is used in the form of Tungsten Carbide, which is put on the tips of sawblades and router bits for cutting into any kind of wood, soft metal (i.e. aluminum, brass, copper, tin), or some kinds of plastics.

The great thing about carbide is you can be abusive with it and it will out last pretty much anything. I've seen people cut aluminum plates with carbide tipped saw blades, which is somewhat slow and careful process, with woodworking ripping blades and it the end the aluminum plates were crappy looking but the sawblade didn't dent, snap, or shatter or anything. It is still cutting wood even today. Carbide on router bits is especially great since it has an incredible durability. Cutting wood with router bits can be very stressful on the bit and normal HSS (high speed steel) bits can easily break or lose their sharpness quickly. Solid carbide and carbide tipped bits never break (unless they happen to run over a metal screw too quickly putting too much stress on the bit and breaking it) or loose their sharpness.

Despite carbide's incredible durability it is very brittle like diamond. So using it in something other then cutting material wouldn't be wise. If your dropped your nice new Carbide Spoon (don't ask), it would shatter like a piece of glass.