As the Nazis took control of Germany in 1930s and turned it into a dictatorship, the German Army, the Wermacht, needed to be rearmed for the Nazi's war. The Heereswaffenamt gave orders for a new small arms. The Karabiner 98k was brought into service in 1935. It was constructed to chamber the 7.92 x 52mm and it could receive the Seitengewehr 98 bayonet just like the Gewehr 98.
In World War II games like Call of Duty or Medal of Honor the Kar98k is the main armament of the German soldiers. It is a very powerful weapon and is capable of taking out any allied soldier from short to long distance by one shot. It is a fire and forget weapon, cause you don't have to care about the target anymore. The sights differ from game to game.