Everything on the linux file system extends from "/". / is the equivalent of C: in Windows. Meaning that for example if you were to delete "/", you would delete every file on your system.
/etc/passwd - Stores user information - Often used to see all the users on a system

/etc/shadow - Has all the passwords of these users
Not showing for obvious reasons
/tmp - Every file inside it gets deleted upon shutdown - used for temporary files

/etc/sudoers - Used to control the sudo permissions of every user on the system -
****https://imgur.com/SEtC1rs Too Long to show
/home - The directory where all your downloads, documents etc are. - The equivalent on Windows is C:\Users\<user>

/root - The root user's home directory - The equivilent on Windows is C:\Users\Administrator
Not showing because of spoiler ;)
/usr - Where all your software is installed

https://imgur.com/e0l4Ybh**/bin and /sbin - Used for system critical files - DO NOT DELETE**
Too big to show, but contains all of the basic programs needed for linux to function
/var - The Linux miscellaneous directory, a myriad of processes store data in /var

$PATH - Stores all the binaries you're able to run - same as $PATH on Windows