File system :

Files are organized in single rooted inverted tree structure. Filesystem begins at root directory, represented by a lone / (forward slash)….
There are many files… said to be scripts are stored in /etc
Medias such as CDs DVDs Pendrives or any external media are stored in /media or /mnt … It is mounted under these two folders.
Home directory for root and other users are …. /root ane /home/username
Kernel and Bootloader information are Stored in /boot
Server data are stored in /srv and /var
System Info. : /proc , /sys


Command
5. pwd - is used for present working directory
6. cd – change directory
7. ls - to list the directory
8. cp – copy files and folders
9. mv – to move or rename files and directory
10. touch – to create empty files…
11. rm – removes ,
12. rmdir – remove directory
13. mkdir – make directory
More options and information you can search by man command