This link may help explain.
http://www.beabetterhitter.com/text/fundamentals/stance.../stanceandvision.htmIt is just one of many resources available. Some of your questions would indicate that you may be fairly new to the search for baseball knowledge. There is nothing wrong with that but please remember you will find many conflicting ideas. Always consider the source, but more importantly, consider the results. I have been very happy with the results my son has gotten from
www.batspeed.com. Others will disagree with Jack and I'd be shocked if they didn't jump in with some help too.