The interoperability of Microsoft Teams and Skype for Business enables users in the same organization to make one-on-one voice and video calls or chat. However, there're some limitations about the interop experience, such as screen sharing (desktop or app sharing), file transfer for two-party chats, and so on. For a richer experience, users may have to know the client that the other side uses. After you apply this update, Skype for Business on Mac and mobile users can be notified that it is an interop conversation when users are in a one-on-one chat or call.
How to get this update
To get this update, install the January 2019 cumulative update 6.0.9319.537 for Skype for Business Server 2015, Web Components Server.