This is pretty basic stuff so you may very well know this already but in the event you don't, for reference here are a couple of images to illustrate commodorewheeler's post above:
Picture #1: Oxford or Balmoral
Picture #2: Derby or Blucher
Generally accepted that a bal is more formal than a blucher. I find that my high volume/high instep feet work much better with bluchers. Therefore, many of my shoes fall into that category.