Question: What is the difference between an apparition and a vision?
Answer: "Apparition" would seem to refer to the act of appearing, or perhaps to the person or thing appearing, while the word "vision" is usually used to describe the method by which the apparition was perceived. Apparitions and their perception can occur in various ways. They may arise from divine, diabolical, or natural sources, and may be perceived with one or more of the senses. The objects may exist in reality or the perception may be impressed directly on the senses or the imagination. Due to the possibility of misdirection from diabolical or natural sources, one ought not act upon what is revealed in a vision without careful deliberation under the direction of one's confessor. One of the best sources of information about private revelations is Adolphe Tanquerey, The Spiritual Life: A Treatise on Ascetical and Mystical Theology (Tournai: Desclee), paragraphs 1489-1515, which can be found on the Internet at Discernment of Apparitions; A. Tanquerey