In case you’re not aware, it’s one of the premier libraries of icons that is used across the web to give websites a little more flare by letting them add icons to buttons, content, whatever really. WordPress uses Dashicons, Bootstrap uses Glyphicons, I use FontAwesome.
You can download and host the files locally, which are subset into Brands, Regular, Solid, Light and the new Duotone. And if you want to auto-subset, they have a feature called Kits which only loads the icons that you need, to reduce page bloat.
As a Pro licence holder, I’ve kind of lost track of what’s Pro and what’s not, but you certainly get a lot more icons, and access to the CDN, if you prefer not to host locally (although I would recommend self hosting personally). There’s also an NPM package, and you can download it as a desktop font.
This plugin, once activated, allows you to reference icons and included them anywhere on your site, either by using the appropriate HTML or using a WordPress shortcode. There’s also the option to tick the “Use Pro” option in order to get access to allow of those extra icons (if your domain is whitelisted in your account).
At the time of writing, the plugin as at the Release Candidate stage, so not fully released yet, but well worth checking out. Even if your theme or plugin already has FontAwesome included, this plugin will attempt to resolve any conflicts, thus allowing you to upgrade your site to the Pro icon set.