What are the type of authentications supported to access a database in .NET?
This kind of authentication is used for an application that works on a windows-based intranet. It uses current windows identity established on OS to access the database. Windows authentication is recommended when you want to avoid storing user names and passwords in database connection strings. You won't be able to use windows authentication when your application and database are in separate domains without trust.
SQL Server authentication
This should be used when Windows Authentication is not possible.