As far as we know, people with paranormal abilities do not exist. Every time you do a well designed test, you don't see any anomalous effects. However, when you do not constrain psychics in the way they interact with their subjects, they seem to be able to tell things they couldn't possibly know. Part of this can perhaps be explained by the psychics getting indirect information from what the subjects are telling them. But non verbal communication presumably also plays a role.
It may be the case that people who seem to have psychic abilities in reality have abilities similar to savants, see e.g. here:
http://www.centreforthemind.com/publications/SavantNumerosity.pdf
E.g., there are people who can look at a screen with a large random number of dots and tell you within a second exactly how many dots there are. There are people who given a date can tell you within a second what day of the week that date falls. They don't consciously compute the answer in their heads. They'll tell you that when they hear a date they can "feel" what weekday corresponds to it.
Neurologists have some idea about how savants can have such abilities. It presumably has to do with them having access to lower level information that normal people don't have access to.
Now, you could imagine that psychics have savant like abilities when it comes to being able to read non verbal information from the faces of people. But then, just like a savant can "feel" the correct number of dots on the screen without counting them, a psychic simply feels the information when looking at his/her subject. They don't consciously do an effort to interpret the facial expressions to try to guess whatever information they are after.
So, to the psychic, it may feel like some ghost is giving him/her the information. They are then not (necessarily) charlatans in the sense that they are not consciously deceiving people; they really believe in their abilities.