Used to identify organic compounds.
Seems to be based on the effects that electrons around the nuclei (shielding electrons) have on the outcome of NMR.
So it is a bit unlike MRI where you are interested in the position of certain nuclei in space (of course, these being atoms, you can't see their positions in space).
What's Nuclear Magnetic Resonance by Bruker Corporation (2020)
Source. Good 3D animations showing the structure of the NMR machine. We understand that it is very bulky largely due to the cryogenic system. It then talks a bit about organic compound identification by talking about ethanol, i.e. this is NMR spectroscopy, but it is a bit too much to follow closely. Basically the electron configuration alters the nuclear response somehow, and allows identifying functional groups.