Font Awesome is an interesting way to add SVG icons to your web project. They allow you add codes into your page which are rendered as icons. Big, small, coloured, animated, flipped etc, they come in all sort of styles. ie, you can customize the icons into a variety of output with a single piece of code.
Font Awesome is primarily an icon font. ie, icon which is added as a font. In effect, you are not adding images, it is icons that you are adding, but the output is images in real. Since those images are SVG, you get a variety of option for screen size as well. ie, it will look well a variety of screen sizes and resolution.
I doubt that whether there is any developer who has not taken advantage of font awesome yet.
What I like more is it's name. Font Awesome is of course an awesome name for icon fonts. With their latest version summing up around a million + dollars on kickstarter project, Dave ( owner ) had his fortune redefined as well. It is always good to see that a free, open source project makes some money as well.