Jan Reid uses her psychic and medium gifts
in a sitting

A Medium is a highly sensitised individual whose heightened sense of awareness can be used to form a link between the deceased and the living.  Sensitive to energy changes.
The spirits of the departed communicate with friends and loved ones still in the physical world through the medium, who is used as a channel to give messages by referring to past events known only by the client, bringing love and reassurance.

A psychic isn’t necessarily mediumistic.  A psychic is a person who uses extrasensory perception to identify information hidden from the normal senses, particularly involving telepathy, clairvoyance, clairaudience and clairsentience or who performs acts that are apparently inexplicable by natural laws. Many people believe in psychic abilities and the word "psychic" is also used as an adjective to describe such abilities. In this meaning, this word has some synonyms, as parapsychic or metapsychic.
A psychic is a person with the ability of ESP (Extra-Sensory-Perception) The word ‘psychic’ originates from the Greek word ‘psychikos’ (Pertaining to the Soul) and refers to the ‘psyche’ (The Human Mind). Most people are probably psychic to a degree and these abilities can be developed with training. A great many people would have had dreams that come true, had the feeling of being somewhere before or many be able to anticipate what someone is about to say. Many believe they have had a contact from a known person who is on the other end of the phone before they answer. Experiments have shown that a great many people will know if they are being stared at and new mothers know when their new-born is distressed When a psychic gives a consultation, this would include intuitively perceiving information about the sitter using clairvoyance (clear seeing) and telepathy (mind to mind communication) clairaudience (clear hearing) and clairsentience (clear feeling). In some cases, this can include information that is already in your mind but also extraordinary information about your situation.

A Clairvoyant (clear seeing) sees objects, actions and spirit beyond the range of natural vision and can also be Clairaudient (clear hearing) and Clairsentient (clear feeling), which means they can hear the voices of the spirits and Clairsentience which means they feel the messages in their own body. This can give the client messages about future events.

Clairaudience is the capability of receiving an intuitive vocal message from the world of spirits or a higher being. Clairaudient people can extend their hearing to transcend the everyday physical world and the known level of awareness, in order to reach the world of spirit.

Clairsentience means a clear sensation an intuitive feeling/sensation through different kinds of physical or emotional stimuli from other people or from the environment.

Another term you may hear is Psychometry and this is where the medium/clairvoyant/psychic has an ability to receive messages through energy/vibration from an item belonging to the client, i.e. a ring/brooch/watch.

And of course in yesteryear (and in some countries still do) any and all of these terms were referred to witchcraft.