As you probably know, there are two kinds of user interfaces out there: graphical user interfaces (GUI’s) and command line interfaces (CLI’s). You probably know that in a GUI you control things by pointing and clicking with your mouse, and in a CLI you type commands with your keyboard.
For example, the ye olde MS-DOS has a command line interface. In the old days the command line was the only interface available on Unix systems, but these days Unix and Linux systems have a graphical user interface, too. Probably you find the GUI easier to learn, at least if you’ve accustomed to the interface of the most popular OS, Microsoft Windows.
Because the Linux command line looks very much like MS-DOS, some people confuse them and think the Linux CLI is just like DOS. Don’t get these mixed! Keep in mind that the Linux CLI is much more powerful than DOS. DOS sucks big time when compared to the Linux CLI!
Another way of getting to the CLI is to leave the GUI completely. You could do this by shutting down the X Window System, but you probably don’t want to do that. Instead, you can just switch to another virtual terminal, while the X Window System is still running. By default, Linux usually has six virtual terminals and the seventh one is where X is running. Pressing Ctrl+Alt+F1 takes you to the first virtual terminal, Ctrl+Alt+F2 takes you to the second virtual terminal, and so on. So, you can switch the virtual terminals by pressing Ctrl, Alt and the function key with the number of the desired terminal.
When you’re in the virtual terminals, you’re not in the GUI (X Window System) anymore, you’re only in the CLI. But although you’re not in X anymore, you didn’t shut it down. It’s still happily running in the seventh virtual terminal, so you can just switch back there normally with Ctrl+Alt+F7.
You probably see a login: prompt in the virtual terminals. However, instead of the login: prompt, you might also see weird text filling the whole screen. Don’t worry, the weird text is just the messages that X is displaying. This is normal and you shouldn’t worry about it. Just switch to another virtual terminal and everything’s cool again.
When the terminal displays the login: prompt, you can just type in your user name and log in normally in the terminal. After logging in you’ll get the same bash shell. Now go ahead and try out the virtual terminals if you want, but don’t forget to come back with Ctrl+Alt+F7.