They are invisible files that contain all the Finder configuration information for each opened window on the computer. If you were to delete them, then they will be recreated whenever you reopen the windows.
In actuality they are ".DS_Store" files beginning with a period which makes them invisible in OS X.
You can't delete me, I've everywhere, in all your folders.
If your seeing these, there is a problem,
Perhaps you used TinkerTool to turn on invisible items, if so then turn them off.
Use the OnyX routine #12 here, that should fix things that is causing that to occur.
The .DS_Store (a.k.a. Desktop Services Store) is a hidden file that OS X creates to store folder attributes like folder icons, background images, and more. By default, Finder will automatically create this hidden file in any folder it accesses. The most common reason that you'd actually see this file in the Finder is that at some point, you've enabled the viewing of hidden folders in the Finder. Do undo this, open Terminal (found in Applications, Utilities) and copy and paste this text that is in bold:
defaults write com.apple.Finder AppleShowAllFiles NO
Then it return on the keyboard. Now type in: Killall Finder
then hit the return key. Now the .DS_Store should be gone.
Hope this helps!