Beam is a streaming service that Microsoft acquired in mid-2016. Like Twitch, Beam allows gamers to stream their gameplay while interacting with viewers via a text-based chat interface. The difference between Beam and Twitch, primarily, is the remarkably low latency Beam has between the streamer and the chat pane.
Beam also has an SDK which allows developers to bake remote controls into their games allowing viewers to interact directly with the streamer's play, should the streamer enable it. Beam also plans to integrate the service with Xbox and Windows 10 before the end of 2016, adding another social pillar to Xbox Live's increasingly diverse network.