There are various ways to make a knife, but all rely on heating steel past a certain temperature and then cooling very quickly (quenching) to set the correct crystalline structure. The steel is heated to 830 - 880' Celsius, quenched,  tempered (to take the brittleness away) and then ground using a series of abrasive belts using gradually finer grits to give the final finish. For bushcraft and kitchen knives particularly, the wooden sides of the handle (the 'scales') are then glued, pinned with brass or stainless rods and tube, and sanded to shape (a 'full tang' knife). This makes for a very strong knife. Some of my knives, particularly reenactment and historical knives, may use a hidden tang where the blade is set into a solid handle, rather than scales. This also applies to the Scottish national knife, the Sgian Dubh.