I really don't understand how clearfix work, anyone willing to explain?

I'm trying to wrap my head around the concept of understanding clear-fix and for the life of me I really can't understand it. No matter how many videos I watch, the concept won't wrap around my head. suggestions guys?

Epic visual tool

Epson 5030UB 2D/3D 1080p 3LCD Projector Submitted October 04, 2015 at 07:25PM by RawadM http://ift.tt/1QSGq1k