What is the significance of "Taxonomy Catch all Column" Lookup column?

What is the significance of "Taxonomy Catch all Column" Lookup column?
https://social.technet.microsoft.com/Forums/sharepoint/en-US/896cea1d-dc40-47f1-80f4-7a01f2d23fd9/what-is-the-significance-of-taxonomy-catch-all-column-lookup-column?forum=sharepointgeneralprevious

Why Do Hidden Taxonomy Catch All Columns Become Visible? - See more at: http://blogs.c5insight.com/Home/entryid/385/Why-Do-Hidden-Taxonomy-Catch-All-Columns-Become-Visible#sthash.FwHFoMNO.dpuf
http://blogs.c5insight.com/Home/entryid/385/Why-Do-Hidden-Taxonomy-Catch-All-Columns-Become-Visible