it's basically when an artist draws a character (or a bunch of similar characters), and sells said character(s) off to someone else, so that the buyer will become the new owner.

A MISERABLE PILE OF SECRETS, HAVE AT YOU!

*tosses wine glass*

*gets squished by wine glass* D:

It's basically someone buys and owns a character made from the artist's work and creativity, basically you make a character to sell it rights to someone else, letting them do whatever they want with the character, and make a buck, this idea started as something to help those with no art skill or a definitive description of what their characters are, allowing them to buy those designs off artists to use them, but it kinda blew up to have a market on it own now xD

Oh, and it does not ALWAYS work (well, it definitely work with famous artists) since we see alot of "Copy-Paste" style characters, like make one character, same pose, but give it multiple colors, selling each color as separate character, baaaad,
Quality character would define how interesting the design is, amusing ideas and features added to it, and remember, simplicity is a beauty, adding stuffs helps alot, unfortunately some before used this big time and ended up making something that looks too much to look at,
Maybe a new race, maybe a new twist to an existing race,
Oh, and art-style DEFINITELY helps, Alot, I've seen VERY boring looking characters being sold for big money purely because the art was awesome... which is kinda sad to me, Atleast.