If you weren't paying attention last week, something crazy cool happened to Lightroom.
It's learning to see.
Call it what you will - smart search, smart image, object recognition, HAL Jr. - the fact is that Lightroom on the Web can now help you look for your images based on a subject or topic you type into the search field, even when that keyword is NOT part of the image metadata.
But let's back up a bit. You might be asking yourself, "Did he just say "Lightroom on the Web?!?"
I did indeed. You see, along with your Creative Cloud Subscription (full membership or photography plan) not only do you get access to the syncing abilites of Lightroom Mobile and Lightroom Desktop, you also have access to any of those synced collections from within a web browser.
In your browser, simply type in lightroom.adobe.com, login with your Adobe ID, and you will see anything you've synced with LR mobile, along with much more.