Font Awesome

Font Awesome provides us with Scalable Vector Icons. They are easy to use, and customizable as well. You may change size, color, drop shadow and many more styles of the icons.
Some of the salient features of the Font Awesome project are listed below:
  • Font Awesome 5 has a PRO edition with 4845 icons, and a FREE edition with 1480 icons and that all with a single font.
  • It's free (as free as free beer).
  • Though it created out of Twitter Bootstrap, it works seamlessly with other CSS frameworks too.
  • Since it does not require JavaScript, browser compatibility issues are minimal.
  • With the help of CSS, you may easily modify the look and feel for eg. Color, size, drop shadow etc. of icons.
  • Since these are based on SVG, they rendering quality is good in all sizes. Font awesome icons look awesome even on high resolution displays.
  • Unlike many other Icon fonts, Font Awesome are screen reader friendly.

Usage
To use the Free Font Awesome 5 icons, add the following <link> element inside the <head> section of your HTML page and display icons by using a class attribute with the prefix has followed by the icon's name.

<head>

<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.6.3/css/all.css" integrity="sha384-UHRtZLI+pbxtHCWp1t77Bi1L4ZtiqrqD80Kn4Z8NTSRyMA2Fd33n5dQ8lWUE00s/" crossorigin="anonymous">

</head>

New in Font Awesome 5 is the fas prefix, Font Awesome 4 uses fa.
The s in fas stands for solid, and some icons also have a regular mode, specified by using the prefix far

Font Awesome is designed to be used with inline elements.The <i> and <span> elements are widely used for icons. Font-size or color changes can be done on the icon using style tag element.