As the crankshaft turns, the pistons go up and down in the cylinders. The timing belt keeps the crankshaft and camshafts connected and in time with the pistons. The camshafts open and close the intake valves, allowing the air and fuel to enter the combustion chambers to be ignited to produce the power. The spent fuel is then exhausted through the exhaust valves. The timing belt is the connection between the crankshaft and the camshafts. If this connection is broken, potentially valves can contact pistons. Worst case your motor could be ruined.
