In parapsychology, the word clairvoyance is used purely to explain information - in the present time and not really readily accessible to the clairvoyant - received from an external source, as opposed to telepathy, where information is transmitted from one mind to a new. In other words, a clairvoyant has the ability to see or visualise events, items or persons away from capability or array of physical sight.
Distant viewing, usually a controlled, specific process, is really a facet of voyance gratuite, as is email dreaming. For instance, a person may dream about a location they've never seen before and later on find it is exactly as they had visualised it in their dream.
This happened to me, for example, when I was about to start my first term at college. As I had never been to the city where the university was located, my pops offered to take myself there in order to find just how from the train station towards the college. Having dreamt about it the night before we went, I used to be able to lead him to the school along the shortest route possible, knowing in which and when to turn. I had been even able to simply tell him how long it would get us to get right now there.
However, outside of the industry of parapsychology the term is often used to describe other types of paranormal, or anomalous, perception. Most of the time, it is used in relation to the perception of past (retro cognition) or even future (precognition) events. This can be a gift many possess without even realising this. To use another personal expertise as an example (and I don't claim to be a clairvoyant in any way), a few years ago, a friend's daughter choose to go into hospital at the start of the evening to have her first child. Although with a group of shared friends around 10 PM, somebody suggested we should phone the hospital and find out just how she was making. As one of them found the phone, I introduced that a call would be wasted, as she had have a little boy in early hours of the pursuing morning. We called anyway and informed she was asleep as the labour experienced slowed. My friend said the next morning which her grandson came to be at 5:30 AM.
Frequently, mediums will also refer to the perception of images recognized during communication together with spirits as clairvoyance.
Whatever the case, clairvoyance is a precious gift which can and should be used in order to help and guide others.