Nuclear magnetic resonance (NMR) is a powerful technique that's used to study molecules and also living things such as humans or yeast (because, after all, we are just a bunch of molecules). NMR allows you to measure different kinds observable quantities that are related to unobservable and interesting molecular properties. One of these observables is known as chemical shift; we can only get chemical shifts for the nuclei of certain types of atoms.
All of this is in the domain of quantum chemistry and the details are irrelevant for this discussion, but let me explain the name chemical shift; shifts because we measured a signal shift from a reference value, and chemical because the shift is related somehow to the chemical ...
