[Verizon Samsung Galaxy S III] SlimSnoopOS:
Whenever you use Odin, it's primarily to return to stock or flash a modified image to your Samsung device. In essence what you want to only use Odin for, is to return to the way you purchased your phone: fresh out of the box. You "should" be on a stock image if that's what resolved your previous issue which led to you creating this thread. In all honesty, I'm amazed that you fixed your phone via youtube. Going forward, all that you need to know about the Verizon GSIII is here: http://xdaforums.com/showthread.php?t=1762709

Stick to using XDA for now.

Nightlies = a new version of that rom is updated each night. Some things may break, some things may be fixed but from nightly to nightly, there are new things introduced and new things broken. A nightly is essentially a prolonged "beta" of the overall rom. You can update from one nightly to another or even choose to update weekly if that works best for you, it's all about choice. Now in regards to CM10, CM10 = CyanogenMod10. This is the most popular Android rom and is supported on the most amount of Android phones. The [OFFICIAL] Verizon GSIII CM10 rom is one rom that is pulling software and improvements that are being worked on hourly by the "lead" or primary CyanogenMod team. If that doesn't make sense, the Verizon GSIII version of CM10 is one branch from the giant, ever growing tree that is CyanogenMod.

The "OP" or original post is the very first post, on the first page of any thread. It is also labeled #1. So, the OP of your thread would be your initial post which I responded to. When reading rom threads, the OP is where all the primary information and download links are. People will use this term all the time. I'm just dropping knowledge on this for future reference.

Usually, developers or respected developers have that title just below their name. For example, look at my name and it does not say "recognized developer." This is a title granted by the awesome people that run XDA to people who apply for this title. If accepted, this is a label that informs new users that this is someone of knowledge. Now, if someone doesn't have this title, then this does not mean they did not develop said rom or that they do not know what they're doing. Anyone can be a developer, but just know that there are people here who will easily put you in your place if you pretend to be one.

The thing about XDA is, you download anything and everything at your own risk. By modifying your phone software, you and you alone voided your warranty and accept this. Now, to answer your question. The OP in any thread that is in the Development or Original Development section is supposed to be a "true and reliable" link. If there were ever a virus or malware posted in the Development section, this is unquestionably a website that will remove it. For any and every phone that has a forum on XDA, there are moderators (or mods) who patrol and work for XDA to keep this place awesome, concise, and welcoming to new and old users alike. If you look at any given world/regional/carrier phone, there are a team of moderators who govern those entire threads. Sure, someone can post a spam link at any time but you should feel relatively safe knowing that there are people in place to control for those things. Now, if you see links ANYWHERE else, then I don't suggest downloading it unless you see others have done so as well and provided significant feedback as well.

This is by no means a rule but if a thread has over maybe 30 pages, then it's something that many others have used. Read a few pages if you have any doubts. The most recent posts about the rom are always at the end of the thread. The CM10 link that you posted has over 600 pages...it's trusted lol. The nicest way to say this is...the most popular roms may be the threads with the most pages.

Also, stick to downloading roms from XDA or Rootzwiki and download only what you feel comfortable with downloading to your phone. You mentioned a youtube video earlier, disregard it and refer to DroidStyle's Guide that I linked after your first question. Rooting may not be for you and that is perfectly fine because this is a hobby. As you can tell, there's a LOT to learn and I've barely scratched the surface.

To properly unlock the bootloader on the GSIII, you need to be rooted first then you need to download EZ Recovery v1.2. I provided and labeled that in a prior post. The "unauthorized software" message occurred because you (I am assuming btw) watched that youtube video from July which predates when our bootloader was officially unlocked (August) and followed its instructions. Since our bootloader was unlocked on August 15, 2012: you must be rooted and unlocked prior to flashing roms or kernels.

You can use that thread to root BUT for the sake of helping you, just download EZ Unlock v1.2 (bootloader unlock tool) that I linked to on Rootzwiki.

Because I do not want to confuse you further, the only bootloader unlock tool you need to know of is EZ Unlock v1.2 which is located on Rootzwiki. If you rooted with your laptop, just install EZ Unlock v1.2 and press "Unlock." You only need to do this one time and can uninstall the app afterwards.

To restore your CWM backup, you need to:

1) Root

2) Unlock via EZ Unlock v1.2

3) Install CWM using EZ Recovery

4) Reboot into recovery

5) Restore your backup in CWM recovery

6) Enjoy your backiup predating the triangle warning "Unauthorized software on this device" incident

Did I cover everything? haha