Throwing knives are knives designed, of course, specifically for being thrown. Throwing knives are normally used as self-defense knives hidden on the person, small and easy to whip out and throw at an attacker. Besides this use, though, today the main purpose of throwing knives are for sport; competition and just fun practicing. I myself have a couple throwing knives, and they are incredibly fun, especially when it sticks point first.
These knives normally do not have any handle material, other than the plain tang, as the knife maker does not want to fashion a brilliant deep brown walnut handle, just to have it knocked off when the throwing knife bounces off a target.
Throwing knives are very much different from other knives. Throwing knives have to be specifically designed so they would have the center of gravity in the center of the knife, just in front of where the handle would end, so that the whole knife would rotate evenly in the air. Otherwise, rotation is very uneven, and this can cause much instabilization and shaking of the knife while it is in flight, and that in turn severely moves the knife off-target. Look at these pictures and try to detect any similarities in design:
When throwing a knife, one of the most vital things is distance from a target. The knife has to make full revolutions to hit point first. For example, you throw a knife from five paces (holding the handle) and it may have only enough space between your arm and the target to make two and a half revolutions, which would mean the knife would hit pommel first. Taking a step back from the target would give enough room for 3 whole revolutions, which means the knife lands point first into the target. A step forward instead of back means room for 2 full revolutions, and thwack, that target is dead.
In a life-death situation, even if you hit pommel first, throwing knives have heavy metal handles, and the concussion would kill the attacker. For self-defense, other than a gun, a good knife would be the best way to go. Simple, useful in non-combat situations, and deadly.