What is it. I see it mentioned often, mostly relating to verifying photos.  
Some help please?

to weed out the fake ads from the real ads. It's not 100% foolproof, but it does narrow down the field.

TinEye is used to do a image search of a picture and/or graphical image.  

If you have installed the TinEye Add-on to your browser, you would be looking at an ad and say to yourself, "This lady looks too good to be true." That's your signal to right click on that picture and click on TinEye and it will do a search for you. If the search indicates that picture was pulled from some other website that doesn't belong to that lady in the picture, then it's a good chance that the ad is fake.

Try it. I use it all the time. It does help a lot!

Click on the link below.

The Forest Waits

The Cut and Paste option:

http://tineye.com/
 

looks like you covered all bases. I will try it.

go to google.com/images, then click the little camera in the search bar, and you will see the option to paste an image URL to see where else online google has found that same pic.

when you right click on a pic, one of the selections will be "Search image on Tineye".  Click on that and it will search for the picture to see if it pops up anywhere else.  

Swim