Here is the difference:
No. .NET Core and .NET 5/6/7/8/9 do not use the .NET Framework reference assemblies. However, if you ever open a legacy *.csproj targeting net45 , you will need it.
During installation, go to the menu
After installation, check:

Here is the difference:
No. .NET Core and .NET 5/6/7/8/9 do not use the .NET Framework reference assemblies. However, if you ever open a legacy *.csproj targeting net45 , you will need it. net framework 45 developer pack link
During installation, go to the menu
After installation, check: