Windows 10 Home and Pro has, right now, two levels of data collection, Basic and Full. When a computer is in Basic mode, Microsoft says Win 10 takes a note of the state of your hardware and its specifications, your internet connection quality, records of crashes and hangs by software, any compatibility problems, driver usage data, which apps you've installed and how you use them, and other bits and pieces.
In Full mode, shedloads more is sent over. It includes everything at the Basic level plus records of events generated by the operating system, and your "inking and typing data." Engineers, with permission from Microsoft’s privacy governance team, can obtain users' documents that trigger crashes in applications, so they can work out what's going wrong. The techies can also run diagnostic tools remotely on the computers, again with permission from their overseers.
In the Creators Update, aka Windows 10 version 1703, all this information will be collected in Basic mode. A lot of it is to help Microsofties pinpoint the cause of crashes and potential new malware infections, although it includes things like logs of you giving applications administrator privileges via the UAC, battery life readings, firmware version details, details of your hardware down to the color and serial number of the machine, which cell network you're using, and so on.
Then there's the information collected in Full mode, which includes everything in Basic plus your user settings and preferences, your browser choice, lists of your peripherals, the apps you use to edit and view images and videos, how long you use the mouse and keyboard, all the applications you've ever installed, URLs to videos you've watched that triggered an error, URLs to music that triggered an error, time spent reading ebooks, text typed in a Microsoft web browser's address and search bar, URLs visited, visited webpage titles, the words you've spoken to Cortana or had translated to text by the system, your ink strokes, and more.