[Sprint LG G3] outofluck:
Sorry for the delay; I didn't receive a notification for your response.

When rooting, the main thing we want is a custom recovery. We want the ability to create nandroid backups which essentially back-up the state of your device's current ROM, Kernel, etc. You want to have a back-up plan in case you mess anything up, and these backups are it. You can flash back to them at any time if you, say, flash a ROM and it won't boot. This gives you something working you can go back to if you get stuck, while you do more research to figure out what is wrong. Now, the G3 came out of left field with a pain-in-the-ass for a bootloader. It is really difficult to crack. And it's taken so long that good ol' Chainfire and his team managed to come up with Bump, which is an exploit to get around the bootloader so we can install a custom recovery (which is TWRP, as I referred to in my post above) and create backups. Having a custom recovery is also what allows us to wipe the internal bits and flash roms and kernels. If you haven't already, reading through the bump thread is a good idea. It has not been fully explained because the team released the exploit too early, and with the lollipop update on the way, the team wants to keep it quiet so LG is less likely to patch it since this is currently our ONLY means of circumventing that pain-in-the-ass of a bootloader. To my knowledge there is not one thread with all the info you desire, but you can check out threads for all of these things individually to see what they are and how they work. Also, what's nice is TWRP looks and works the same for many devices so you don't really need to stick to specifically LG G3 related TWRP discussions to learn about what it is and how it works. It's important that you read LG G3 specific info about it when it comes time to flash and makes backups, since in my experience, you have to wipe everything except for the internal and external storage before flashing (which is something not all devices have to do, such as my old HTC I mentioned) when flashing.

Stump is an exploit which allows you to gain root. SuperSU is the app from Chainfire that actually allows you to USE root. Apps need to request root permissions, and SuperSU is the app that allows for this. So, for example, if you install Titanium Backup (also an invaluable app for us tinkerers) to freeze or backup any of your apps, it will request root permissions, and you'll see a pop-up from SuperSU asking whether to grant or deny this request. Bump is the exploit to get around the bootloader and making backups/flash ROMs and kernels. TWRP is the custom recovery where you perform the backups, flashing, and so on.

This stuff takes some time to absorb and understand, especially for someone new to the entire set-up. My advice is to take your time and read as MUCH as you can on just about everything. It becomes easier after you flash a ROM or two. And you'll probably **** up once or twice along the way. Just make sure you have your backups and you'll be fine.

I also did a quick search and I found this article. It's a bit old but a lot of the information is still relevant and it might just help you feel a bit more confident about rooting your phone in general: http://lifehacker.com/5789397/the-always-up-to-date-guide-to-rooting-any-android-phone

My personal recommendation to you would be to (if you haven't already done so) hold off on rooting for a little longer until you feel less confused (DO NOT ACCEPT ANY UPDATES IN THE MEANTIME), and when you're ready, look into getting rooted, create a nandroid backup of your stock ROM as it is so you have a clean slate to return to if things go wrong, and then check out the ROM Barren. Engine95 took the stock ROM and cut out all the Sprint and LG bs that isn't needed. Some cool customizations should be coming along the way too, such as theming. He has the SD card thing I mentioned in my other post fixed too so you don't need to worry about that. That's what I'm currently running and it's definitely a bit smoother and more battery-friendly than the stock ROM is by itself. Here's the thread: http://xdaforums.com/sprint-lg-g3/development/rom-barren-odexed-deodexed-t2916085