What Does It Mean When Your Foot Pronates When You Walk Or Run What Does It Mean To Over-pronate?

What does it mean to Over-pronate? - what does it mean when your foot pronates when you walk or run

I'm pretty sure that the feet are flat, but I still see an arch in the foot, compared with pictures of flat feet is a big bow. When I run or walk, I have pain in my feet and sometimes shin splints. Now I'm looking for a pair of shoes, new balance, more likely, and I keep seeing the term in pronation. What does this mean?