.NET Core is a free open source, a general-purpose development platform for developing modern cloud-based software applications on Windows, Linux, and macOS operating systems. It operates across several platforms and has been revamped to make .NET fast, scalable, and modern. .NET Core is one of Microsoft’s big contributions and released under the MIT License. It offers the following features:
Cross-Platform Open Source High Performance Multiple environments and development mode etc.
.NET Core is to be used for the server application when –
There is cross-platform need. Targeting microservices or using Docker containers. Need of high performance and scalable systems. Side by side need of .NET versions per application. .NET Framework is to be used for the server application when –
Application is to be built to run only on Windows. If application uses .NET framework technologies not available for .NET Core. Applications that are already running on .NET Framework.
source : https://www.geeksforgeeks.org/differences-between-net-core-and-net-framework/