Overpronation is something that get thrown around a lot in the running and running shoe communities as a cause of running injuries and as a method to prescribe running shoes. There are so many myths and nonsense about the whole conceort. For started watch this video:

A lot of those myths and nonsense can be seen in that video. Overpronation is not evil and plenty of people overpronate and never have any problems, other overpronate a little and have big problems. It is all going to be individual. “Overpronation” has a lot of experts and it is hard sometimes for teh average person to know what is correct or not with some many internet “experts”. Some of the advice is good; some of it is not.