The Advanced Communications add-on was recently released for Microsoft Teams. This is a set of features you don't get with your regular E3 or E5 licenses.
So what do you get for $12 per user (have in mind, only organizers of meeting need these licenses in order to use them).
- Live events support for up to 20,000 participants, 50 concurrent events, event duration of 16 hours per broadcast.
- Compliance recording integration (ISV)
- Contact Center solution integration (ISV)
Coming later, but obviously in the works:
- Interactive Teams meetings for up to 1,000 participants
- Interactive Teams meetings for 1,000 participants with the capability to enable up to 20,000 in a view-only meeting experience
- Custom branded meeting lobby
You can read more about the advanced licenses in the Teams documentation