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 , text , concept maps , and combinations of the foregoing . through the use of concept maps and icons that control modes of output of information , a user may navigate the domain of knowledge and retrieve information specific to the user &# 39 ; s particular needs .