Clairvoyance and remote viewing refer to the same phenomenon- the ability for one person to see something, occurring at that exact moment, through means other than the five senses. Along with telepathy, it is one of the two major forms of Anomalous Cognition (gaining information without the five senses). The existence of this phenomenon has never been scientifically proven.
The term clairvoyance is often differentiated by the fact that it does not occur in a controlled environment. This leads to even more difficulty in ascertaining its existence.
In the early 1970s, the U.S. Central Intelligence Agency (CIA), and later the U.S. Air Force, began funding experiments to test the existence of remote viewing. It lasted until the mid 1990s. At that point, the data was analyzed. Some test subjects had scored above simple chance, however, it was not by a great deal- 10 to 15%. Additionally, the methods of testing were called into question. Ultimately, no consensus could be reached as to whether remote viewing existed, and it remains unproven.