Crowd Computing is a Minecraft mod that allows a streamer's audience to participate in a constructive, controllable fashion. With the streamer's permission, the audience is able to perform a wide variety of useful tasks, both manual and automated.
The flagship use case of this mod is a streaming pack called Crowdsourced, which uses it to provide the vast majority of its content.
You probably don't need me to say this, but since I work there, I need to say it anyway: This is not an officially supported Google product. Nor is it a Google product at all. It's just a personal project of someone who happens to work there.