Its a confirmation that the npub has a connection to a secondary website. It can be used as a call out, for instance i am wedgesocial@nostrplebs.com 

The idea behind it is that if it said beth@ftx  for the verification you knew they were affiliated with that company. You will notice @jack has removed his as that account is verified by other means and doesn’t really tie to a commercial entity. 

 Thanks for explanation! Any secondary website, for anything, anywhere. Just another source of verification proving one’s identity or affiliation with xyz. 

 Thanks Dan, for this detailed explanation! Much appreciated 

 Apparently it has to do with verification— I’m guessing like a blue check on X ? 

 I think that’s right, yes.