Q. What telemetry is gathered in Windows 10 and what control do I have?
A. Windows 10 is the most connected version of Windows to date and that can be a concern for some who want to understand the exact data and how identifiable that data is. Microsoft have a great article at https://technet.microsoft.com/en-us/library/mt577208%28v=vs.85%29.aspx which walks through all the telemetry gathered and used in Windows 10 and the ways it can be configured/disabled. Definitely worth reading.