Recently I came home after a long drive and when I turned the ignition off, the engine kept on running! I called a friend and he told me about the stop button in the engine compartment, but had no idea what caused the problem. Whats the problem?

This is indicative of a vacuum problem. Did your power brakes stop working as well? There is a vacuum switch connected to the ignition switch which is resposnsible for shutting the motor down. If this switch goes bad your car won't shut off. If your other vacuum run components stopped working as well, check the door lock elements (these are vacuum powered as well and stop working as well. Also check the vent elements (these are also vacuum powered) Good luck!