Primary information is one of those terms. "Information" isn't often defined in the genealogical literature and we'll save a discussion of that for another day on the Rootdig blog. However, primary information is information obtained from someone who had first hand knowledge of the information they are conveying. Ideally, they are sharing that information while their memory is accurate. Any other information is said to be secondary.
Whether a given piece of primary information is correct is another story.