A psychic is any person who has some level of mastery over their innate ability to ‘tune in’ to energy. Clairvoyance is one specific area of psychic. Clairvoyance means clear seeing. So a clairvoyant is a person who sees images, pictures in ones mind’s eye as a form of communication with spirit. In a sense there is no difference in the outcome of a message, per se, except that the method or technique used to get the message will differ. A psychic could see, hear, feel; or sense the message whereas a clairvoyant only sees. Only seeing has its drawbacks in that it prevents the ability to hear. Hearing spirit is called clairaudient. So, a psychic uses ‘tools’ to translate subtle energies to which they are sensitive to.
A medium, on the other hand, is more a vocation than a description. A medium’s only purpose is to prove life after death by communicating with loved-ones who have passed over. To this end a medium will give clear and accurate proof, such as names and details of the spirit they are communicating with. A Medium will prove life after death, and to do this they will use psychic skills such as clairvoyance etcetera.