It's reliability of the information. If you tell me something, then I can go and say that I believe because you told me, as I have first-hand knowledge. If you're telling me something as a result of a meeting that occurred with you and some other people, that is a little less reliable, because it may be based on third-party information, etc. If I am an affiant and I have personal involvement in the events that I'm swearing to, I have information and belief. If I don't and I am relying on an informant, for instance, it may be different.
On March 25th, 2010. See this statement in context.