the current directory changes to the "documents" subdirectory. If you now type:
You will see the files and subdirectories in the "documents" folder. (The terms "folder" and "directory" have the same meaning in this context.)
If you want to go one level up to the parent directory of the current directory, you can can type:
The two periods mean "parent directory".
You can also go several directories down or up in one step:
This, will go to the "receipts" directory, which would be a subdirectory in the "documents" directory.
Similarly, you can go two levels up with this command:
Depending on the directory tree, you can move through any path of this tree in one step:
This will first go one level up, and then two levels down.