text: The engine that connects some pieces of information (e.g. ones about the initial state) with some others (e.g. those about the final state) is completely different in classical theories and in quantum theories. But the information is ultimately the very same thing. We make a measurement and we learn some information from that procedure. Information is whatever distinguishes one's state of ignorance (or knowing less) from the state of knowledge (or knowing more). In general classes of situations, information may be quantified, too. But there's no point in trying to decompose the words "information" or "know" to words that are more elementary. There are no words that would be more elementary. One must understand at least some words if she wants to be able to say anything about anything. Attempts to "define" words like "know" inevitably end as a ludicrous worse-than-circular game that "decomposes" simple enough words into words that are much more complex, contrived, or subtle or several of these adjectives at the same moment.