This is an in-class group exercise. Do this with everyone in your group.
Introduction: Some information is in your head. It's memorized. Examples: your email address; how to ride a bike; what stop signs mean; what underlined blue text means. It's important to note that knowledge in the head need not be precise (which is awesome), and that it often encodes social/cultural constraints.
A lot more information is in the world. It's not memorized; you access it when you need it. Examples: your professor's email address; what type of tires your bike has; whether and where you should stop at a given intersection; a typical URL. Information in the world is (often) precise and can provide the precision not available in your head - think spelling autocorrect. Information in the world can also be encoded as physical constraints - think limits on how far you can turn a steering wheel or which way to turn a jar lid.
For those interested in background reading, Norman devotes all of chapter 3 in The Design of Everyday Things (Norman) to this topic.