What is a trance medium?

A trance medium is someone who can let a spirit take possession of their body, the way Sylvia Browne was able to.  Trance channels also channel a variety of different sources of information.  I’m a claircognizant trance medium, who can channel about subjects I haven’t read much about.  I have grandpa’s agricultural knowledge in my head, rattling around in there.  I also have my own knowledge, whole books, articles, libraries, and wow, just a lot of different kinds of information in my head, and lately because of Mr. hernia, I have had to limit how many webinars I go to, books I read, and even classes I take.