The root bridge is used for STP stability in u r layer 2 network where u have redundant links.The root bridge is the reference point for all of u r switches.if u have redundant links in ur enviorment u may have stp loops if one of the link in not blocked.so the non root switches are going to block one of u r redundant link by using the paramters of the root bridge .i.e u r avoinding loops in u r network.
