insertion loss and return loss

hie..
can any1 please explain what exactly is return loss and insertion loss of a filter?
Thanks alot

Insertion loss is the decrease in transmitted signal power resulting from the insertion of a device in a transmission line or optical fiber. It is usually expressed relative to the signal power delivered to that same part before insertion. Insertion loss is usually expressed in decibels (dB).

Return loss is the ratio, at the junction of a transmission line and a terminating impedance or other discontinuity, of the amplitude of the reflected wave to the amplitude of the incident wave. The return loss value describes the reduction in the amplitude of the reflected energy, as compared to the forward energy.