What really is reactive power?

I understand reactive power as being the energy stored in an inductor or capacitor in the form of a magnetic or electric field, and it is a result of the phase difference between an AC current waveform and its corresponding voltage waveform. However, I am not confident in this concept. I am interested in understanding it better in an electrical distribution/power system. Can someone please explain?

Also, I have read on many websites online that reactive power is important in regulating voltage in a power system and providing gird stability.

How does reactive power affect grid and voltage stability? What happens if there is too much or not enough reactive power on a system?

Thanks