On stackoverflow i read about runtime&sdk and as i get

Question

On stackoverflow i read about runtime&sdk and as i get

it, the difference between runtime and sdk shortly is, first for running aps, second for building and running aps. But I ran next command
dotnet —list-sdks
and there only net 6.0
when
dotnet —list-runtimes
lists as net 3.0, net5.0 and 6.0

Then I see that in Visual Studio I can create aps with net 3.0, 5.0 and 6.0
When I don't have sdk 3.0, 5.0. Then he uses only runtime then or there is something else?