Some operations require more privileged authentication — for example, if any user could invoke the transfer mutation, they would be able to transfer as many NFTs as they wanted to themselves, so we probably only want the application to be able to initiate that operation!
For operations that should only be initiated from the app or app admin's context, we support two forms of privileged authentication.
Backend authentication amounts to your application authenticating as itself, instead of in the AppUser context.
In some situations, you may want members of your development team to log into your application and perform privileged operations. Most of these operations can be handled in the Admin Portal, but you can also authenticate your team members as AdminUsers instead.