Say that we have a circuit with a power supply and an inductive load on it. From the instant that electrical power is supplied to the circuit, the inductive load will accumulate stored energy. If an attempt is made to open the path with a switch, this energy will generate a high reverse voltage and arc across the contacts of the switch. This could damage the switch, load and other circuit components.
A freewheeling diode placed across the inductive load will provide a path for the release of energy stored in the inductor while the load voltage drops to zero.