Affordance - A visual clue to the function of an object. Examples of affordance might be a sliver plate on the side of the door that you need you need to push to open it or a "raised" look on a button on a website.
Androgogy - Refers to the instruction and training of adults (people who are not in school anymore).
Cognitivism - A learning theory. Learn more about cognitive science.
Constuctivism - A philosophy masquerading as a theory. A way of looking at the world that says that people construct their view of the world based on their previous experiences. People construct their own unique knowledge from raw materials. Learn more about constructivism.
Instructional Theory - Specifications for how to bring about a desired set of circumstances. Technological. Compare with Learning Theory.
Instructional Design Theory - How to design/create artifacts. This includes tools for design.
Learnability - how easy is it for the user to learn how to complete the processes needed within the system. Learnability can be tested by exposing the user to a system and then bringing them back later to see if they still understand how to complete a task. Learn more from Usability 101.
Learning Theory - An attempt to describe how people learn. Examples include constructivism, behaviorism, and social cognitivism. Scientific. Compare with Instructional Theory and Instructional Design Theory. Comparison of learning theories.
Model - Simulations or prototypes. Models range from an equation, to a sketch, to a full size product.
Multi-user Dimensions (MUDs) - A very popular format for gaming are Multi-user Dimensions. MUDs are also used in educational or training simulations
MOOs (Multi-user Object Oriented programs) -
Multi-user Virtual Environments (MUVEs) - A MUVE is a user interface that attempt to create a virtual environment for presenting information. This is an interface that is often in video games. See an example.
Prototype - a prototype is a physical model of a product. A miniature version of what a new car would look like is an example of a prototype. Prototypes can be working or non-working.
Simulation - a simulation is a virtual model of a product. A simulation is essentially the same thing as a prototype, but it generally uses some sort of software to create the product virtually.