[HTTPS-Everywhere] What does "([^/:@\.]+)\" and "$1" do?

[Victor Garin]

When I started, I used the below rule as an example, because it used
to encrypt all the subdomains:

<ruleset name="Netflix">
  <target host="netflix.com" />
  <target host="*.netflix.com" />
  <rule from="^http://([^/:@\.]+)\.netflix\.com/" to="https://$1.netflix.com/"/>
</ruleset>

I assumed it also encrypted the main domain, but that doesn't seem to
be the case for example here:

<ruleset name="FaxZero">
  <target host="faxzero.com" />
  <target host="*.faxzero.com" />
  <rule from="^http://([^/:@\.]+)\.faxzero\.com/" to="https://$1.faxzero.com/"/>
</ruleset>


i.e. browsing to http://faxzero.com does nothing?

What does "([^/:@\.]+)\" and "$1" do?

Is there a way, to write in the same line, to redirect the main domain
to https also? Or does the main domain rule, have to be in a new line?