What is this Linux mode called?

Question

linux

When I press ctrl+alt+f1...f7 I get to the terminal or go back to the GUI.
1) What are the names of these things that I switch? Consoles?
2) Why are there 7 of them and is it possible to change their number?
3) If I install debian without a graphical shell, then I have only one console and I cannot switch. I want to install on an old debian laptop with no graphics and be able to switch between multiple consoles. How can I do it?

Answer 1

2) you can change if you really want - https://askubuntu.com/questions/1124397/how-do-ii...
3)

I only have one console and I can't switch

- unlikely. I work with a bunch of servers - always works.

Answer 2

You need tmux

Answer 3

1) Terminals. In an era when computers were large pieces of iron, they were connected to them from terminals (conventionally, this is a stupid keyboard). The device /dev/tty* is associated with the terminal. An external connection to the system (session) is always associated with some terminal.
2) It happened that way.