This was the most fascinating discovery to me, so I thought I would share it in hopes that it makes your day too - before you "pin" something, use your cursor to highlight a description of the item on that site, then click the pin icon in your tool bar, and wa-lah! Automatically that highlighted description will appear in the pop up box!
Try it out - it is very neat and convenient! Do you know any other pinterest secrets? [besides that it is fabulous!]