Understanding the core components of .NET
.NET has two major components: a runtime and base class libraries. The runtime includes a garbage collector (GC) and the just-in-time (JIT) compiler, which manages the execution of .NET applications and base class libraries (BCLs), also known as runtime libraries or framework libraries, which contain the fundamental building blocks for .NET applications.
The .NET SDK is available for download at https://dotnet.microsoft.com/download/dotnet/5.0. It contains a set of libraries and tools to develop and run .NET applications. You can choose to install either the SDK or the .NET runtime. To develop .NET applications, you should install the SDK on the development machine and the .NET runtime to run .NET applications. The .NET runtime is included in the .NET SDK, hence you don't have to install the .NET runtime separately if you have already installed the .NET SDK: