The bindings between input events and commands are recorded in data structures called keymaps. Each binding in a keymap associates (or binds) an individual event type either with another keymap or with a command. When an event is bound to a keymap, that keymap is used to look up the next input event; this continues until a command is found. The whole process is called key lookup.
NOTE: Keymap documentation has not been completely updated for XEmacs. Some of the information below is incorrect.