What is the major difference between the natural frequency and the damped frequency of oscillation.​

This causes the amplitude of the oscillation to decay over time. The damped oscillation frequency does not equal the natural frequency. Damping causes the frequency of the damped oscillation to be slightly less than the natural frequency

Any second order or higher order dynamic system would have a unique property called the natural frequency of oscillation. A frequency at which the system tends to oscillate when disturbed. Though, when a damping element is introduced into the system, the system's unique undamped natural frequency changes a little bit, according to the value of the damping coefficient. This involves some math, which u will have to read somewhere more academic.