.NET, ASP.NET Core, and C# are all components of the same ecosystem but they serve different purposes. Here's a brief comparison of these three:

.NET (Framework and Core):

• .NET is a software development platform developed by Microsoft that provides services and tools for developers to create different types of applications, ranging from web to mobile to Windows-based applications.
• It includes an extensive class library called Framework Class Library (FCL), a Common Language Runtime (CLR) for executing applications, and various other components for development.
• .NET has two primary implementations: .NET Framework and .NET Core.
• .NET Framework is Windows-only and has been around since 2002, while .NET Core is cross-platform (Windows, macOS, and Linux) and open-source.
• As of .NET 5, Microsoft has unified the .NET platform, merging .NET Core and the original .NET Framework into a single .NET platform that can be used for a variety of application types.

ASP.NET Core:

• ASP.NET Core is a framework for building web and cloud-based applications and it's a part of the .NET platform.
• It's a redesign of the older ASP.NET 4.x, built to be cross-platform (Windows, macOS, and Linux), high-performance, and open-source.
• It can be used to build anything from small, single-page or multi-page web applications to large, enterprise-scale web applications.
• It supports different development models, including MVC (Model-View-Controller), Razor Pages, Web API, and Blazor for building interactive client-side web apps using C#.

C#:

• C# (pronounced C Sharp) is a modern, object-oriented programming language developed by Microsoft and is often used in the .NET environment.
• It's statically typed, supports both reference and value types, and provides syntactic support for many features, including garbage collection, exception handling, and more.
• C# is used to write applications of all types and sizes with .NET, including console apps, desktop apps, web apps, mobile apps, cloud services, and more.
• The syntax and design of C# make it relatively easy to learn, particularly for those with a background in Java, C++, or other C-based languages.

So in a nutshell: .NET is the platform, ASP.NET Core is a framework on that platform for making web applications, and C# is one of the languages you can use to write applications on the .NET platform or with the ASP.NET Core framework.