Flour used in the starter

Hi guys 

Been away from making breads for a while after getting lazy and letting my starter die, got a new starter to the point its ready to bake with. I notice a lot of people use different flour types in there starter, my last starter was just 100% white bread flour and I've done the same this time, just wondering what the advantages are of using different flours in your starter? 

And secondly am I able to add in new flour to my original white flour starter to change it or would I have to start the process again with a different flour? 

Always been blown away by how knowledgeable and supportive people are in helping newbies like myself out on the fresh loaf so thanks in advance for any help.