Abstract: A computer system having an explanation facility for facilitating user understanding of concepts underlying a domain of knowledge which enables a user to interact with and explore the domain of knowledge. The explanation facility utilizes a concept-map based representation of a domain of knowledge and several icons to control the mode of output of information from the computer system. Each concept map has concept nodes which represent concepts in the domain of knowledge, links between the concept nodes, and icons. The icons are positioned at the concept nodes and represent alternative modes of output of information from the computer system. A user desiring more information about a concept node can select one of the icons corresponding to the mode of output of information desired. Modes of output of information include audio, video (images and movies), text, concept maps, and combinations of the foregoing.