Anyone willing to show me a visual example of how clear fix work?

I been trying to wrap my head around the concept on how clearfix work, however I can't seem to understand the concept. Help would be appreciated.

I have created a pen so someone can help me understand it. In this example I'm working on the navigation. When I float the list items left the navigation collapse. That's when clear fix fixes the issue, however I don't understand it just yet.

http://ift.tt/1R2JyLe

Epic visual tool

Epson 5030UB 2D/3D 1080p 3LCD Projector Submitted February 03, 2016 at 06:28PM by RawadM http://ift.tt/1PSno9a