Limits access to the site to people on an allowed list of IP addresses.
Only people on the allowed list can see your site. Others will see a customisable "Coming Soon" style of page. To remove protection, simply disable this plugin.
You'll get a new admin screen that lets you view the allowed list, and remove IPs from that list. The content that people not on the list see is fully customisable through the admin screen.
Useful when you're working on the site, but aren't ready for the public to see it. Primarily, I use this for client sites. I develop the site, allow the client to see it, then remove this plugin when we're ready to launch it.