Psychics were once considered the way to see the future or communicate with the spirit world. Even today, there is still a large part of the population which works with them, or appreciates them well enough to pay for their services. The shows that have supernatural elements have some of the largest audiences, and these are the things psychics know.
Magic and sorcery were practices modern religions sprung from and this is because of their capacity to answer questions from the human subconscious. At the very least, psychic mediums provide some need for comfort that no other profession provides. And they are often authentic or simply earnest in their belief in the spirit world and magical stuff.
Some psychics rely on some scientific tenets, although science itself calls them fake or pseudo science. Whatever labels exist, the medium can be one very magnetic personality, perhaps because of the vibrations that surround her or him. These cannot be discounted as fake, and though science has taken up the challenge of disproving these notions, so far it has been unable to do so.
Religion have now stopped the prosecution of magicians, although there were centuries in which the prosecution was intense. Even so, many have survived to propagate the belief in things like the undead, mummies, wolverines that speak in the night, changelings, lupine tribes and vampires. The psychic is simply a person who channels all the associated magical forces for information.
In this sense they provide data which anyone may use or not use. It all depends on the circumstances, although there are many of the sanest people who have encountered supernatural experiences they could not explain with reason or science. These have provided much impetus for the business of psychics.
They are also much sought after in certain groups that also practice their own brand of magic. The mediums channel spirits and let their clients talk to them, and no one really knows which ones are real, even with some hidden set ups. Because nature and the universe are not really systems that science or reason knows.
There are sites that address the subject, and also provide good information about how they work and what signs you can see as belonging to the supernatural. Divinities can be contacted too and so much have conflated over the years, that there may even be angry gods of ancient and supposedly dead religions abroad. The medium can tell which of these are present in psychic situations.
Also, they will tell you that the world is very changeable, and no one knows who or what controls the physical present, or whether there are really boundaries with the past. Or if time is really represented by the 12 hour clock. So many mysteries exist that some experts in this line limit themselves to card reading or fortune telling with some magical boards.

Even these are mysterious enough, and a lot of people have experienced calling on spirits with an empty glass and a paper filled with letters. You alone can tell which one fits your needs, keep faith to, without looking at anything else that might be offered. Most of this time, there can be some deeper meaning related to the subconscious that this expert can provide.