What is 'ServicePrincipalName parameter represents Microsoft.Web RP in user tenant' ?

I don't get where this ServicePrincipalName parameter comes from? Could you explain, please?

I'm working on a template and I need Microsoft.Network to access key vault, where can I get this ServicePrincipalName?

Thanks,
Alex

Start by locating the template that defines or uses the ServicePrincipalName parameter and trace how it relates to Microsoft.Web and Microsoft.Network access to Key Vault. Document where the value comes from and how a user can obtain the appropriate service principal name for this scenario.

Written by the indexing model from the issue text.