00000.MTS and 00000.xmp . . . what the @%$£**&+":**^ !

I copied the whole AVCHD file structure from my SDHC card onto my desktop over Christmas.

Today I happened to open the folder and to my surprise I discovered that every .MTS file had a corresponding .xmp file as shown in the screenshot.

These files were apparently created 5 days ago by Photoshop Elements and presumably by me!

Unfortunately I can't recollect what I was doing so can anyone shed any light on what these files are?