Depending on how you got your copy of Windows 10, you'll need either a 25-character product key or a digital license to activate it. Without one of these, you won't be able to activate your device. The product key or digital license can't be substituted for one another.

• A digital license (called a digital entitlement in Windows 10, Version 1511) is a method of activation in Windows 10 that doesn't require you to enter a product key. If you upgraded to Windows 10 for free from an activated copy of Windows 7 or Windows 8.1, you should have a digital license instead of a product key.
• A Windows product key is a 25-character code used to activate Windows. 
• This product will be delivered electronically