describe-key

describe-key is an interactive compiled Lisp function in `help.el'.

It is bound to C-h k, <f1> k, <help> k, <menu-bar> <help-menu> <describe> <describe-key-1>.

(describe-key &optional KEY UNTRANSLATED UP-EVENT)

Display documentation of the function invoked by KEY.
KEY can be any kind of a key sequence; it can include keyboard events,
mouse events, and/or menu events. When calling from a program,
pass KEY as a string or a vector.

If non-nil, UNTRANSLATED is a vector of the corresponding untranslated events.
It can also be a number, in which case the untranslated events from
the last key sequence entered are used.
UP-EVENT is the up-event that was discarded by reading KEY, or nil.

If KEY is a menu item or a tool-bar button that is disabled, this command
temporarily enables it to allow getting help on disabled items and buttons.