The "Shared" folder in an ASP.NET Core MVC project typically contains the shared Razor views like layout and error pages. These views can be reused across multiple pages, providing a consistent look and feel to the application.

When a user is not authorized to access a specific action, ASP.NET Core returns a default HTTP status code of 401 Unauthorized. This status code indicates that the request lacks proper authentication credentials or the provided credentials are invalid for the requested resource. It's a fundamental part of the authentication and authorization process in web applications.

Georeplication is a strategy that ensures high availability by deploying application instances in different geographical regions. This approach minimizes downtime in case of regional outages or disasters, providing a robust and fault-tolerant architecture.

When you see a generic "An error occurred" message during development, it might be because Debug Mode is disabled in your ASP.NET Core application. Enabling Debug Mode provides detailed error information to help developers diagnose issues.

For reusability, developers can create Razor Components, which are similar to partial views but with more logic encapsulation. Razor Components encapsulate both the UI and the code, making them highly reusable and self-contained.

To make a tag helper available across all your Razor views without adding its namespace to each view individually, you can use the element in the _ViewImports.cshtml file. This centralizes tag helper configuration for the entire directory, making it accessible to all views within that directory.

The "Startup.cs" file in an ASP.NET Core project plays a crucial role in configuring middleware and services for the application. It defines how the application will handle requests, set up routing, and configure various components like authentication, logging, and dependency injection. It's essentially the entry point for configuring the application's behavior.

ASP.NET Core introduces a built-in Dependency Injection (DI) system, which was not part of traditional ASP.NET. In the past, developers often relied on third-party libraries for DI, but ASP.NET Core brings this critical feature into the framework, making it easier to manage dependencies in your applications.

The dotnet CLI (Command-Line Interface) allows you to install NuGet packages from a local feed or folder. It provides the dotnet add package command, which supports specifying package sources. This is particularly useful when working in an offline environment or when you want to use custom package sources.

To get started with ASP.NET Core development, the primary software you need to install is the .NET SDK (Software Development Kit). This kit includes the necessary tools, libraries, and runtime environments to build, test, and run ASP.NET Core applications. Visual Studio Code is a popular code editor but does not include all the components required for ASP.NET Core development.