1) nything below .NET 5.0 we call it as “.NET Core”.

2) .NET 5.0 is the next major version of .NET Core.

3) The current latest version of .NET Core is 3.1 and of .NET Framework is 4.8. Version number 5 is greater than both hence the name .NET 5.0

4) They have skipped version numbers 4.x to avoid confusion with .NET Framework 4.x.

5) They have dropped “Core” from the name to emphasize that this is the main implementation of .NET going forward. .NET 5.0 supports more types of apps and more platforms than .NET Core or .NET Framework.

Refer this great answer : https://docs.microsoft.com/en-us/shows/One-Dev-Minute/What-is-the-difference-between-NET-Core-NET-5-and-NET-Framework--One-Dev-Question