http://philosophy.eserver.org/hegel-summary.html
DEFINITION
1. 'Phenomenon' is a word which refers to appearances. It's a Greek word used by Plato to distinguish mere temporal appearances from the eternal Noumena of the Ideal Realm. The student of philosophy should recall Plato's parable of the shadows in the cave, where appearances were taken for realities. Phenomena are appearances. Where is the reality? In Hegel's view, probably unique in Western Philosophy, we can only know Reality when we have completely mastered the appearances, since the appearances (phenomena) partially hide and partially reveal Reality (noumena, Geist) in a peculiar manner.
2. There are degrees of reality within various phenomena. This is the origin of Hegel's idea that there can be degrees of truth in propositions. There are material phenomena and there are mental phenomena. Phenomena of mind also partially hide and partially reveal the truth. The study of phenomena is called, phenomenology, and Hegel focuses on mental phenomena, hence the title, PHENOMENOLOGY OF MIND.