This is very retro text effect where you have a text and on hover, the alpha channel gets split out and appears as text-shadow around the text. This was designed by ilithya.
You don’t learn to walk by following rules. You learn by doing, and by falling over.
Richard Branson
If you are having trouble with the pen, try the archived copy on GitHub
Text Shadow Hover Code Snippet
See the Pen Hover Alpha Effect by ilithya (@ilithya) on CodePen.default