Test-Driven Development (TDD) is a software development methodology where tests are written before the actual code. Developers write small, focused tests that guide the development process, helping ensure that the code meets the requirements and is thoroughly tested.

The UserManager class in ASP.NET Core Identity is a vital component for creating, updating, and managing user accounts. It provides methods for tasks like creating users, assigning roles, and resetting passwords, making it an essential part of user management in ASP.NET Core applications.

The 'FindByEmailAsync' method of UserManager can be used to check if a user with a specific email address already exists. This method searches for a user with the given email and returns the user if found.

The "Controller" in the MVC design pattern typically receives user input in ASP.NET Core through HTTP requests. It listens to incoming HTTP requests, extracts user input data from the request, and then processes it to determine the appropriate action to take.

When creating a user programmatically using ASP.NET Core Identity, the CreateAsync method typically returns an IdentityResult object. This object can be checked to obtain detailed information about the reasons for the failure, such as validation errors or other issues encountered during user creation.

To set up a new ASP.NET Core project with built-in user authentication, you should choose the "Individual User Accounts" template. This template provides user registration, login, and other authentication-related features right from the start, saving you development time.

Unit testing is the practice of testing individual components or units of software in isolation from the rest of the application. It helps identify issues within these units before integrating them into the larger system.

You can override the default layout specified in the _ViewStart.cshtml for a specific Razor view by using the @layout directive in the view file itself. This allows you to customize the layout for a particular view without affecting the application-wide layout defined in _ViewStart.cshtml.

When creating a custom Tag Helper in ASP.NET Core, the class should derive from the built-in TagHelper class. This base class provides essential methods and properties for working with HTML elements and attributes within Razor Views, making it the foundation for creating custom Tag Helpers.

You can specify a different layout for a specific Razor view by using the Layout property within the Razor view itself. This allows you to override the default layout defined in the _ViewStart.cshtml or any other global configuration.