They are preference files used by applications. I know it is quite the surprise, given that they are in a folder named "Preferences"....
I just found in my preferences folder some strangely named files.
com.elgato.eyetv.plist.42KTas4
Size is 0 kb.
What are these? Maybe these are created when Mac crashes?
Common issue and you can delete all the ones with the gibberish at the end. What is happening is when you save preferences it creates a temp copy of the file to save the changes to, and there is a bug where that temp file is not getting erased after the save operation.
You can see a few here on my system. To me, this seems to be much less frequent under El Capitan.
View attachment 610487
I was not suggested deleting everything in my screenshot. I was just showing a shot with some of those files. The ones with gibberish are all empty and can be deleted. Even if you deleted the real plist (com.apple.spaces.plist in my shot) it would be recreated when you launched the app. If you had an app that would not launch after this, you may have deleted something else.it hasn't happened to me in years, but (just mentioning this), i had a dozen of those plists for an app, deleted all the 'oddly named' ones, and the app would not open, i had to re-install it. my feeling is, the last-opened one is important (and, in the case of your image, the one without gibberish at the end IS the last-opened one...).