Each second order system has a dumped oscillatory response(that is a sinusoid whose amplitude decrases exponentially with time).
exp (-t/T) * sin (wt)
If the time constant T of the exponential term is long in comparison with the period of the sinusoidal term then the circuit is underdamped and oscillation appears in the response.
as T reduces the oscillations die out more quickly and the response becomes overdamped.