1.Answer to the question.........

Remote sensing is broadly classified into two categories. They are Passive remote sensing and Active remote sensing. Passive Remote Sensing : It is used as an existing source of EM energy and records the energy that is naturally radiated and or reflected from the objects.

2.Answer to the question........

In supervised classification the user or image analyst “supervises” the pixel classification process. The user specifies the various pixels values or spectral signatures that should be associated with each class. This is done by selecting representative sample sites of a known cover type called Training Sites or Areas.