Q: How does the System Center 2012 Configuration Manager User Device Affinity work?
A: System Center 2012 Configuration Manager is focused on the user rather than the device. This allows users to have a consistent experience no matter what machine they use, and applications are delivered in different ways based on the current device the user is utilizing.
One of the decision criteria for the method of application deployment is if a machine is the user's primary device; this is indicated through User Device Affinity. There are often questions how this process actually works.
User Device Affinity can be manually configured through the Assets and Compliance workspace and through Devices. Select a device, and click the Edit Primary Users button, then select the user who is the primary user, as the screen shot shows.
Users can also add their own primary devices through the Configuration Manager web portal via the My Devices tab if the option to allow users to specify their own devices is enabled in a policy setting.
Automatic User Device Affinity can be enabled by modifying the Client Settings policy (either the default or by creating a new policy). Under User and Device Affinity, change the default No to Yes for the device and/or user settings. It's important that the Audit account logon events and Audit logon events are enabled on computers too, as these are used to determine the device affinity.
More information can be found at the Microsoft article, "How to Manage User Device Affinity in Configuration Manager." If you want to set the device affinity during OS installation see the TechNet blog "Configuration Manager 2012:User Device Affinity and OS Deployment" for details.
You might also take a look at "Intune and Configuration Manager: Better Together."