If you are trying to restore an Apple iPad, you may receive an iTunes warning that the iPad is locked with an Apple ID. In order to restore the iPad, you will need to unlock the iPad with the correct Apple ID. The email address associated (Apple ID) will be show in the iTunes Activation Lock message.
This iPad is linked to an Apple ID. Enter the Apple ID and password that were used to setup this iPad.
Ultimately, you will either need to contact the previous owner to unlock the iPad with their Apple ID or request an author unlock from Apple. Apple typically will not process an unlock by default and you may need to show proof.
For anyone else that is able to bypass the iPad Activation Lock, please share in the comments section below.