This Skype consumer federation capability will enable Teams users to chat with and call Skype users via their email addresses and vice versa.
The lack of Skype consumer federation is an example of a feature that some users said were keeping them from moving to Teams. Last year, I asked Microsoft more than once if and when the company planned to enable this much-requested feature and was told the company had no comment. In July last year, Microsoft finally said the company would be adding the ability for Teams and Skype consumer customers to communicate using chat and calling in the first calendar quarter of 2020.
One point worth noting: Microsoft has decided that Teams-Skype interoperability will be disabled by default.
"Admins who wish to enable this feature will need to go to Microsoft 365 admin center > External access and Enable users to communicate with Skype users," Microsoft officials advise in the Office 365 Message Center.