Circuit Simulator - Blocking Inductive Kickback (with diodes)

When current flows through the inductor it creates a magnetic field around the inductor when the current stops the magnetic field collapse back through the winding of the inductor. This generates a voltage across the inductor as the voltages induced on each winding is in series with one another.

V=l* (di/dt).

Can anybody please tell me what is inductive kickback and why is that capacitor used in that circuit?