Would it ruin the engine on 2003 Kia Sedona if timing belt broke?

Once there were no timing belts, there were only internal timing metal chains and the owner would never even have to know about it. Then, external timing belts were introduced which are built of special plastics. A timing belt or timing chain allows the engines's valves to close and open at the proper time meaning they are syncronized. If such syncronization is not achieved it could happen that the piston in its upward trust could hit a valve that is open and should be closed breaking metal parts which in turn would fall into the running engine and cause havoc and destruction. Timing belts are built to last only a certain number of miles (many are built to be changed at 20000 miles). If the manufacturer's limit is surpassed, the belt may fail and break with catastrophic effects on the engine. The timing belt's life depends on the manufacturer's specifications thus the car manufacturer's manual will state the number of miles after which it needs to be changed.