They are TTYs, they're like terminals your computer spawns at boot time that you can use. Their intended purpose is really whatever you need them for. I use them for if I somehow mess up my display configuration and I need to access a terminal, but I can't launch my DE/WM.
Ctrl+shift+V is what you should do. Ctrl+V is used by shells for I believe inserting characters without doing some sort of evaluation. I don't remember the specifics though, but yes Ctrl+shift+V to paste.
It's not sideloading, it's installing. Stop giving into this idea that installing other apps is somehow bypassing normal methods!