What in SharePoint 2010 uses the Windows Enterprise Rights Management Service?

An error is appearing within the web front ends of our farm indicating that there was an problem trying to find the enterprise rights management services server.

I had not ever heard of it before, and it isn't configured into my farm in Central Admin. I don't know if we even have such a server.

What actions within SharePoint by users would result in the system looking for such a server?

Thanks!