On this page I will be listing the best bits that I have with a little bit of description so you can get the idea what they're all about.
HTC One X STOCK ROMS
Stock ROM is nothing else than a full operating system that allows a device, like a phone, tablet, to run. ROM is very alike to a disk image for a PC - you can restore a PC from such an image and so you can do with a smartphone. Stock in this case means that the operating system is as it was developed by the manufacturer or by the carries. Stock ROM = like from the factory.
Stock ROMs come in 3 basic forms:
1 - RUU (ROM [Read-Only Memory] Update Utility) - an exe file (Windows app) that contains the ROM itself and a GUI which allows for an easy and painless installation. RUU is the official HTC way of delivering full ROMs.
2 - Flashable ZIP files - files prepared by HTC enthusiasts, flashed to a device in "custom recovery" mode. Those ZIPs are specially prepared and contain system partition structure along with all the files needed. Flashing those ZIPs is really easy and quite safe (you really need to try hard to brick your device). Above all a ROM in a ZIP form = like from the factory.
3 - Nandroid backup files - nandroid backup is (usually) a full backup of the system created in the "custom recovery" mode. One of the most popular solutions for custom recovery are CWM (Clockwork Mod) and TWRP (Team Win Recovery Project). You can google and learn more about those two and other. If the backup is well-prepared (e.g. backup of a clean stock system not with installed extra apps or personal data) it can be flashed to another matching (same) device.
So which for is best for you?
RUUs are hard to obtain especially with the latest system versions. And they are even more rare if you have a branded phone. To be able to use a RUU you must find a file that is specifically designed for your CID (carrier ID number) - otherwise you will fail. But if you are lucky this is as "official" as it gets.
Flashable ZIPs are the best option if you want to debrand your phone or just update to the latest system version and be sure not to have any private data of someone else. In this case the ROM you want to flash does not have to be intended for your CID. However remember - flashing a ROM for a different CID means that you will not be able to use official OTA even if the ROM is stock. An OTA always checks CID and it will not match.
Nandroid backup is great if you have a branded phone and you want to revert to stock after using a custom ROM. Nandroid backup can be used just like flshable ZIPs - there are different files and procedure but basically the result is the same. Just be careful abut personal data - nandroid backups may contain some and normally that is not too good. Choose trusted sources.
Version numbering and additional info.
HTC uses rather simple numbering and the higher the number, the "fresher" the system version.
Sometimes, with a major system update (like from 4.0.4 to 4.1.1) HTC requires to update the phone's HBOOT (bootloader - the initial piece of firmware that starts everything else). Usually it means some security updates but I never was any downsides of a HBOOT update. The important thing is that if a new system update require a HBOOT update as well, there is no way around it and you cannot use a new system with an outdated HBOOT. And unfortunately HBOOT can only be updated by official HTC files - OTA or RUU. So if you want to flash the latest ROM that needs new HBOOT you will have to wait for official OTA or RUU for your CID. Unless you have a S-OFF device (google it).
ODEX vs. DEODEX
If you look into the (stock) system folder of your Android phone you will notice that there are some files with .odex extension. From what I know those files allow for "caching" apps and making the whole GUI work faster. On the other hand ODEX files make it hard to customize the appearance of the GUI. So if you plan to do a lot of visual tweaks with your phone I suggest DEODEXed ROMs. And if you can't be bothered then use ODEXed - I do it that way.
STOCK ZIP files
STOCK nandroid backups
TUTORIALS and DEMOs
Check out my YouTube channel to find useful videos on dealing with your Android device and more.