► .Net Standard is a specification for implementing the Base Class Library (BCL). BCL contains classes such as exception handling, XML, collections, I/O and networking. WPF, WCF and ASP.NET do not form part of BCL and so are not included in .NET Standard library.
► .NET Core is a managed framework that builds desktop and web applications in cross-platform.
► Both ".NET Core" and ".NET Framework" include .NET Standard for BCL in their managed framework.
.NET Framework is a framework that builds desktop and web applications in Windows only. It is highly dependent on the architecture.