user3267: When you create a new wallet, there are 4 options, one being 'hardware wallet'. However, there is no mention of hardware wallets in the docs!
http://docs.electrum.org/en/latest/search.html?q=hardware&check_keywords=yes&area=default

How do it work? Does it communicate to the hardware wallet with a special protocol?

user55974: Yes, it does. There's a detailed guide on the Ledger site, and a bunch of videos on youtube explaining how to use your Ledger with a Electrum.

3267: <p>When you create a new wallet, there are 4 options, one being 'hardware wallet'. However, there is no mention of hardware wallets in the docs!
<a href="http://docs.electrum.org/en/latest/search.html?q=hardware&amp;check_keywords=yes&amp;area=default" rel="nofollow noreferrer">http://docs.electrum.org/en/latest/search.html?q=hardware&amp;check_keywords=yes&amp;area=default</a></p>

<p><a href="https://i.stack.imgur.com/7Ku2c.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7Ku2c.png" alt="electrum wallet selection"></a></p>

<p>How do it work? Does it communicate to the hardware wallet with a special protocol?</p>
 55974: <p>Yes, it does. There's a <a href="https://ledger.zendesk.com/hc/en-us/articles/115005161925-How-to-use-Electrum-with-your-Nano-S" rel="nofollow noreferrer">detailed guide on the Ledger site</a>, and a bunch of videos on <a href="https://www.google.com/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=2&amp;cad=rja&amp;uact=8&amp;ved=0ahUKEwjcxrfd-YDYAhUW8mMKHX7lCZMQtwIILjAB&amp;url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DwfuvuvCZYEE&amp;usg=AOvVaw0F8JHl4ApbAo5oyiApuy2j" rel="nofollow noreferrer">youtube</a> explaining how to use your Ledger with a Electrum.</p>
