Market equilibrium occurs when both the quantity demanded and the quantity supplied are equal. The market equilibrium is shown graphically where the supply curve and demand curve intersect.

An example that I can think of where a market was not in equilibrium was when the COVID vaccine was first released. The demand way outweighed the supply available. People that wanted to get vaccinated couldn't because there just wasn't enough available. In order to bring the market back into equilibrium they needed to produce much more of the vaccine. Interestingly enough they then ended up with the opposite problem - they had so much supply and the demand for the vaccine was no longer there. There were large quantities of the vaccine that expired because the demand was not as high as it once was, so it was wasted. I feel like this was probably created by a number of people that weren't sure about getting the vaccine and were kind of waiting to see what happened with the virus as well as the effects that the vaccine had on people. It's really hard to know for sure as the media around COVID was extremely confusing.

This is just one of many examples that COVID had on supply and demand. I remember stores running out of toilet paper, feminine products, food, water, etc. What a crazy time we had to live through.