David isn't far off. Clairvoyance is to receive extrasensory impressions, mental images, and symbols in their mind (without using their physical eyes. The easiest ways to gain visual information is generally after we have reached an alpha state and during meditation, though many of the more developed clairvoyants can also gain visual information just by concentrating.
Yes there is such a thing as natural born clairvoyants. Everyone is born with gifts. During life, there times where their gifts start to bloom. It can be early onset or late depending on themselves. There are methods that help them to use their gifts: awareness, meditation, balancing, cleansing, etc.
What about clairaudience? I know it's similar to clairvoyance only with hearing not sight. But what exactly do naturally born clairaudience people hear? And what can they expect to happen when this ability begins to manifest in a very real way?
Well from what Ive heard, people with the gift I clairaudience usually hear messages from a higher power, whether it be spirit guides or the divines or maybe just other people. I mean I wasnt born with clairaudience so this is pure theory so I cannot answer your last question.