X-ray function on Kindle?

Okay. So, I kinda drowned my kindle in the smallest amount of water possible when I slipped getting out of the bath–not a good idea to take it too near water, people!–and bought myself a replacement and upgrade, going from a Kindle 4 to a Kindle Paperwhite.

I’m still getting used to it and stumbled across the x-ray feature. I’ve seen it mentioned on Amazon as having “x-ray enabled” but don’t quite get it. So I was just wondering if anyone could help me?