<p>The <a href="http://www.erlang.org/doc/" rel="noreferrer">Erlang documentation</a> contains the documentation of modules.</p>

<p>Where can I find the documentation of the Erlang shell? (Which is not a module, I suppose.)</p>

This page in the documentation
seems to be a starting point. Especially the link in it. Check also the
first link
in it, with the shell's manpage.