In most movies hackers are shown in front of a screen that somewhat resembles the following image:
Usually it is nothing more than a command line/terminal/console/prompt. This is a tool that allows users to control the computer by using text-based commands. So instead of clicking on a folder to see the contents, you just enter a command on the command line (in this case ls). You can also use the command line to edit text files, move and delete files, download pages from the internet, install programs and many more things. Basically everything you do with your mouse you can also do with the command line (except possibly drawing). Developers (and hackers) use it because often you are a lot faster if you just have to enter text and don't have to switch to the mouse all the time (this is assuming you know the commands).
So follow the chapter "Introduction to the command line interface" in the official Django Girls tutorial so you can learn how to use it as well!