Built-in help

Emacs provides many help features, all of which are helpfully bound to a prefix key, C-h.

Basic Commands

[C-h C-h] (or M-x help-for-help)

Provides a list of all help options and prompts you to enter one of the options.

[C-h k] (or M-x describe-key)

Prompts you to enter a key sequence and then provides information about what it does.

[C-h c] (or M-x describe-key-briefly)

Prompts you to enter a key sequence and then displays command that key sequence runs.

[C-h w] (or M-x where-is)

Given a command name, it displays a list of key sequences that could be used to invoke that command.

[C-h v] (or M-x describe-variable)

Prompts you to enter a variable name and then provides full documentation of that variable, including the current value of the variable.

[C-h f] (or M-x describe-function)

Prompts you to enter a function name and then provides full documentation for that function.

[C-h d] (or M-x apropos-documentation)

Prompts you for a list of words or a regexp and then returns a list of functions, variables, etc. that match.

[C-h b] (or M-x describe-bindings)

Displays all key bindings

[C-h i] (or M-x info)

Displays info tree for Emacs

There are many more help commands available. Enter C-h C-h in emacs for a full listing.