Reamping, re-amplifying, is a good way to add excitement in a track. Lets say you have recorded drums in your on rehearsal space with a minimal amount of room sound. Then we run the drums through loudspeakers in the live room and record the ambience with a set of microphones. When mixed together with the original, dry, drum tracks it will give the impression of a natural ambience on the tracks.
Or you can reamp for special effects. Say you have a lined synth track that doesn’t really pop out in the mix. Run it out to an old tape recorder for some tape saturation or possibly even tape delay. Or reamp dry bass track to a bass amp and record that back into protools. The possibilities are endless.