Presentations are the basis of many of the higher-level application-building tools that use accept to get input and present to display output. A command that takes arguments as input specifies the presentation type of each argument. When a call to accept is made, CLIM establishes an "input-context" based on the presentation type. This input context is used to determine which presentations will be sensitive to mouse clicks. For instance, when a user gives the send-tuition-bill command, the input context is of type "student," so any students displayed--both those being displayed for the first time and those that have been displayed before--are sensitive. This is because presentations that have been output in previous user interactions retain their semantics; that is, CLIM has recorded the fact that a student has been displayed and has saved this information.
Common Lisp Interface Manager 2.0 User's Guide - 7 Aug 2017