I have noticed when looking at hidden OS files in some of my PC's directories, not necessarily OS (c drive) directories, there are files with the little gear icons on them and the files are called thumbs. What are these files used for?

Thumbs.db is a small file that caches thumbnail images. That way, when you get to that specific directory, thumbnails appear more quickly. They're never larger than a few kb, and you can delete them if you want. They're not crucial or important. In fact, you can easily set up Windows to not create any new thumbs.db files.

-Open up My Computer
-Click on tools -> Folder Options
-Click on the View tab
-Check the box that says "Do Not Cache Thumbnails"
-Click OK or Apply to all Folders
and you're done!

Now that is very interesting. The only reason they concerned me was because they showed up unhidden in my web server's directories when I uploaded entire folders at once and not individual images/files but were hidden on my PC. Then I was able to see them on my PC when unhiding OS files. I didn't know if they were critical OS files or not. Thanks for the quick reply and explanation!

You're welcome!

I had the same question a few years ago when I saw those same thumbs.db files pop up on my zip disks. I kept deleting them, and they kept coming back! Thankfully, I've learned a thing or two since, so I'm not as concerned when I see 'em.