WHAT DOES BEING IN RESONANCE MEAN
Suppose that the hydrogen protons are cyclists, the precession frequency (wo) is the frequency at which they are pedaling and the water bottle is the energy. When two cyclists (a and b) pedal at the same frequency, the bottle can be transferred between them. It is said that a and b are in resonance. If they were pedaling at different frequencies, one would go faster than the other and they could not transfer the bottle between them. It is then said that they are not in resonance.
To be able to capture the energy of the RF pulse, the frequency of the administered electromagnetic wave (wr) should be the same as the precession frequency (wo) of the protons. On the other hand, the excited protons will release the captured energy faster (relaxation) if wo is similar to the frequency of the environmental molecular movements (wc). Thus: wr = wo = wc