My experience and personal belief is that a spirit guide has lived at some time or another on Earth in a physical body, while an angel has never had a physical incarnation. Every medium I know has one or more guides who work with them — some are constant, and some change during the medium’s life, but each has their own unique influence over the development of the medium’s gifts.
After drawing your cards, revisit your initial question to ensure that it has been addressed properly. A good tarot guide can help you interpret the images you see on the tarot cards, but there’s really no substitute for personal reflection. As with any skill, practice makes perfect, so use this tarot tool often (daily, if possible), or order a set of Astrology Answers Master Deck Tarot Cards and practice at home!