Starter = Sourdough?
I have some questions for starter for so long. First, I would like to know if starter refers to sourdough. If I see 'starter' on a recipe, should I just use sourdough? I usually make breads with instant yeast or dry active yeast, and I don't really know much about starter. I tasted some breads that are made from starter and found them are special. I live around UC Berkeley. I would like to know where to buy 'starter' and how to keep it. I heard that starter can keep long long time if it's being take care well. How to take care of it? Thanks a lot!