Detection is the process of recovering the modulating signal from the modulated carrier wave.
Explanation of Detection with the help of a block diagram:
The modulated carrier wave contains frequencies wc ± wm. The detection means to obtain message signal m(t) of frequency wm.The method is shown in the form of a block diagram. The modulated signal is passed through a rectifier. It produces rectified wave [fig.(b)]; the envelope of which is the message signal. The rectified wave is passed through an envelope detector, whose output is the required message signal m(t).