GNU Emacs Lisp Reference Manual
Chapter 19: Keymaps
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.