The best way to learn is to try things. As long as you aren’t root (and haven’t yet created any important personal files), you cannot mess up too seriously. Jump in—type each of these commands at the prompt and press Enter.
pwd
One directory is always considered the current working directory for the shell you’re using. You can view this directory with the pwd command, which stands for Print Working Directory. pwd prints the name of the directory you’re working in—probably /home/yourname.
ls
ls stands for “list,” as in “list files.” When you type ls, the system displays a list of all the files in your current working directory. If you’ve just installed Debian, your home directory may well be empty. If your working directory is empty, ls produces no output, because there are no files to list.
cd /
cd means “change directory.” In this case, you’ve asked to change to the root directory.
pwd
This verifies that you’re working in the root directory.
ls