I find many who are confused about fiber. Which do we need? What do they do? Both are very important and this article will clarify it nicely for you.
http://www.webmd.com/diet/fiber-health-benefits-11/insoluble-soluble-fiber?page=1
http://www.webmd.com/diet/fiber-health-benefits-11/insoluble-soluble-fiber?page=1