Workplace Join is a tool in Windows Server 2012 R2 that allows a Windows 8.1 device to gain access to specific network resources.
Workplace Join is a self-service tool. When an end user downloads and installs the Workplace Join client on a device, the client asks the end user for a corporate email and password, which is sent to a Active Directory server to be verified. The server then calls or texts the user at a pre-designated phone number and asks the user to confirm that the device in question should be given "join" rights. Technically, Workplace Join creates a new device object in Active Directory and installs a certificate on the device.
The Workplace Join app, which is free, only allows Windows and iOS devices to join the AD at this time. It is expected that Android devices will be supported in the near future.