$ ls # list files
$ man ls # tell me about "ls"
$ cd ~ # change to my home directory
$ cd .. # change to parent directory
$ pwd # show me the current directory
$ mv file.txt new_name.txt # move (or rename)
$ cop file.txt file_copy.txt # copy
$ rm file.txt # remove (delete) file
$ df -h # disk free space, human readable form
$ du -sh . # disk usage, summary, human readable