Explaining the Science bits

I'm not a scientist. I'm not a scientific person. My last science class was about 10 years ago and it was in geography. I've never taken a biological, chemistry, or physics class in my life. I'm not bragging. I do feel that I'm missing out. My point is that this doesn't give me an advantage when it comes to translating scientific things into lay terms. It doesn't mean I can't do it or can't understand it, but it often takes a bit of extra effort and reading about the topic. I'm happy to put in the work, but it also delights me when I find explanations of things (terms, events, theories) that are comprehensible. Today, I found it very challenging to come up with a thorough definition of thermal expansion. It seems pretty straight forward, right? Things (not necessarily gasses since they can be compressed, or so one website told me) expand as they warm. It has something to do with the particles that make up the things moving at more rapid rates and needing more space to do so. My brain imagines this as particles bouncing off one another at an increasing speed meaning that the bounce back sends them further apart, and thus you have expansion. Whether or not this is the case, I cannot tell you. I am still searching for a thorough definition. If you have one, please share. Your help is appreciated. Bet one of these books would do it . . . .