Microsoft Stream is a cloud service licensed on a per user subscription basis. It is available as part of eligible Office 365 subscriptions. The Stream Add-On allows Office 365 users to utilize the full functionality of Microsoft Stream, normally enjoyed only by E1, E3 and E5 users. The Plan 2 Add-On includes all the video streaming and collaboration features of Plan 1, combined with the ability to find more videos using deep searches, based on in-content signals like speech to text. and allowing the user to Interact with video content in richer ways using face detection and audio transcripts.
Access Stream via the app launcher, or at stream.microsoft.com