A combat knife is balanced specifically for hacking and stabbing from the hand. It's almost scary how much a KA-BAR feels like it should be swung. I got mine and as soon as you have it in your hand, it's like it wants to be swung and slashed with. Their perfectly built for making kills at close range. Single-edged with an often thick spine, they are optimal for making very lethal, singular wounds and in knife fights.
A throwing knife is designed to be thrown, held by the tip.
EDIT: Some are balanced to be thrown by the grip as well. For many throwers, I imagine it varies by preference.
They're generally lighter and thinner, so they can go between ribs easier, and are double edged, rather than single edged, so they are more likely to make a cut when thrown. They are balanced to give as much control as possible over the weapon when throwing it.
This doesn't mean that you can't use one in place of the other. There was one guy on the show Time Warped who could pick up anything
that had one light end and one heavy end and throw it point first at any distance within his throwing range. Screwdrivers, needlenose pliers, etc.
Likewise, just about anything can be used to kill someone up close. But, the two knives are designed for a separate function from the get-go.
If anything, get the proper name for it, the KABAR.
The standard KA-BAR is built for slashing and stabbing, useful in a fight against an opponent who is also armed with a knife.
The grip is widest in the center, allowing you to swing the weapon without losing it because your fingers wrap around the grip's wide center, locking it in place.
The hand guard is there to help stop an opponents knife from shearing off your fingers.
The blood strip will prevent suction from blood in an opponent's body grabbing hold of your blade should you stab them. I covered that a few posts up though.
The lower portion of the edge is serated. This is actually a utility feature. It's harder than hell to cut rope with an unserated blade. Those serations are just for cutting stuff that a straight edge is slow on.
The front of the tip curves, giving slashes an nice, smooth laceration.
The spine of the tip tapers down, angling forward. This is all to faciliate a faster, deeper stab.
Many throwing knives lack the strong grip (Or any real grip at all, with many just having the plain tang), guard, and singe edge, favoring sleek, double-edged, slim designs to make a successful throw more lethal and improve aerodynamics.