Not clear on the difference between semolina flour and other flour -- most importantly, where do I get it?
Semolina is coarsely ground durum wheat flour, typically used for pasta. Although it does have other uses, it is not good for baking. My grocery store carries it. You could also try natural food stores.
I get it from King Arthur flours. They have just about any type of flour you can imagine. Their website is bakerscatalog.com
I usually buy it in Whole Foods. Any reasonably equipped grocery should have it. I like to use it for fried foods such as pancakes or tortillitas -- it usually produces much crispier final product than when using general purpose flour.
I have a package almost right in front of me from Bob's Red Mill in Oregon. Popular brand in health food (hah!) stores. I like use it for really authentic Roman dishes, such as gnocchi alla romana.