What is the difference between a body that simply reflects the light that falls upon it and a body that absorbs and emits it (like a black body in thermal equilibrium)?

How can one experimentally distinguish these two scenarios by simple measurements? (I think that reflected and transmitted light do not change the temparature of the body where as emitted and absorbed light do. Is this correct and is it possible to experimentally tell the difference between emission and reflection using this information?)

And what are the mechanisms behind reflection and emission? ( I think emission is related to the electron transissions. But how does a photon decides whether to be reflected or transmitted if it is not absorbed ? )