.Net Core

.Net

.Net Framework

.NET Framework is a Windows-only version of .NET for building any type of app that runs on Windows.

.Net Core

redesigned version of .NET that is based on the simplified version of the class libraries

.NET Standard

Used for building libraries that can be referenced from all .NET implementations, such as .NET Framework, .NET Core and Xamarin.

The "Core" branding was removed and version 4.0 was skipped to avoid conflation with .NET Framework.

.NET Framework 4.8      2019-04-18	
.NET Framework 4.7.2	2018-04-30	
.NET Framework 4.7.1	2017-10-17	
.NET Framework 4.7	2017-04-05	
.NET Framework 4.6.2	2016-08-02	
.NET Framework 4.6.1	2015-11-30	
.NET Framework 4.6	2015-07-20	
.NET Framework 4.5.2	2014-05-05	
.NET Framework 3.5 SP1	2008-11-18

.NET Core 1.0	        2016-06-27 
.NET Core 1.1	        2016-11-16
.NET Core 2.0	        2017-08-14 
.NET Core 2.1	        2018-05-30
.NET Core 2.2	        2018-12-04
.NET Core 3.0	        2019-09-23
.NET Core 3.1	        2019-12-03
.NET 5	                2020-11-10

.NET	        5.x	C# 9.0
.NET Core	3.x	C# 8.0
.NET Core	2.x	C# 7.3
.NET Standard	2.1	C# 8.0
.NET Standard	2.0	C# 7.3
.NET Standard	1.x	C# 7.3
.NET Framework	all	C# 7.3