Function: info-lookup-symbol

Display the definition of SYMBOL, as found in the relevant manual.
When this command is called interactively, it reads SYMBOL from the
minibuffer. In the minibuffer, use M-n to yank the default argument
value into the minibuffer so you can edit it. The default symbol is the
one found at point.

With prefix arg a query for the symbol help mode is offered.
(fn SYMBOL &optional MODE)