Terminal and shell are two very different concepts, though the separation is not obvious to the uninitiated (and the exact location of the separation is a little strange).
- The terminal mainly provides a way to type and display characters.
- The shell mainly provides a way to execute commands.
I recommend using terminal only for questions that are related to the terminal (emulator) and its configuration. Using this tag for “how do I do X on the command line” feels wholly counter-intuitive to me. I recommend keeping a separate command-line for this purpose.
The command-line tag should be used for questions that ask if or how something is done using the command-line as opposed to the GUI. The terminal tag is concerned with questions about the terminal iself, that is what you see when you press Ctrl+Alt+F1. When the question is specific to gnome-terminal or konsole, these tags should be used instead.