An authentication provider is a system or application that holds the user name, password, or other information that Smart Build Insight uses to make sure that the person trying to log on is allowed to do so.
The information that each authentication provider uses to do that might be different. For example, one provide might require email address and password, and another might require a user name and pin number.
That means the boxes you see on the Add User dialog box can change depending on the authentication provider you pick.
For more help, see Give a person access to Smart Build.