The document discusses several topics related to information efficiency and understanding, including: 1) Information efficiency is achieved when people don't have to think, as exemplified by the successes of Google and Apple's iPod. 2) Understanding something means generating meaningful expectations about it. 3) Perception and cognition involve both bottom-up, data-driven processes and top-down, hypothesis-driven processes interacting. 4) The level of description that maximizes information efficiency is when something is understood in terms of its abstract role or relation to other objects, rather than its surface-level attributes.