Many helpful commands that, at a quick glance, 90%+ work on just about every distro of Linux:
A cheat sheet of the commands I use most for Linux, with popup links to man pages.
cheatography.com
A brief explanation of disks in Linux:
A rather brief study of the Linux filesystem:
Back in 1996 I learned how to install software on my spanking new Linux before really understanding the topography of the filesystem. Don't repeat my mistakes.
www.linuxfoundation.org
And then you should know that the file system on SteamOS is immutable - in that all the system files and the main system-related folders can't be modified or renamed. Also, I think it's a good to point out that everything is considered a file in Linux, even devices - so even your hard disks are basically just interactable files that are "mapped" to the physical (or in some cases virtual) disks. In other words, your internal drive, any SD card you may insert, will just look like a file to Linux. Thankfully having to understand how to work with disks isn't really needed if you're just doing things like installing apps or configuring an emulator.
Linux is an extremely straightforward and easy OS to use once you grasp the core basics, and in doing so recognize the obvious differences between it and Windows. Until then, yea, I can see how it would seem completely foreign. Hopefully the above helps. After that, learning to install apps or whatever on SteamOS is just a google search away. Good luck!