An overheating engine is a common sign that your car is low in coolant. A blockage in the cooling system, loss of coolant or failing electrical cooling fans can cause overheating. It's possible a mechanic can repair the engine, instead of rebuilding or replacing it, if the issue is addressed quickly.
A loss of fluid is the more common cause of failure and this happens through a slow leak or a sudden one when an old hose breaks or the radiator develops a leak. The difference in a "blown" engine and one that overheats is evident in the color of the smoke or steam. If blue, it is probably smoke from the burning oil.