Press ? (or, with number_pad on, h) to access the in-game help.

You will see the following menu:

a - Long description of the game and commands.
b - List of game commands.
c - Concise history of NetHack.
d - Info on a character in the game display.
e - Info on what a given key does.
f - List of game options.
g - Longer explanation of game options.
h - List of extended commands.
i - The NetHack license.
j - List of wizard-mode commands.

The last option is only available if the game is in wizard mode.

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