S1 last vs S2 last

can someone explain to me the difference? and why I would go one way or the other?

If you are talking about New Balance shoes…here’s a chart

http://www.joesnewbalanceoutlet.com/customer_serv/about_NB_pop.htm?pop=y&popWhat=last.

thanks. I wanted to know how that made a difference, the chart explains it well. I am trying new shoes, it’s tough!