_photoTarget

The target location to show one of a List of Photos -- Function
LIST OF PHOTOS PROPERTY -> _photoTarget
When you have a List of Photos, you usually don't want to show all of them full-sized on the page. Instead, you usually want to show one full-sized Photo somewhere and some thumbnails; when you click on a thumbnail, it should change the full-sized Photo. That is what _photoTarget is for.
When you pass a List of Photos into _photoTarget, it displays only the first Photo in that list. But if you display the thumbnails somewhere else on the page like this --
LIST OF PHOTOS PROPERTY -> _thumbnail
Then whenever a user clicks on a thumbnail, it will replace the full-sized picture. This way, you can have a lot of Photos, but only take up a bit of display space on the page.
It is legal, but usually pointless, to use this function with Required or Optional Photo; it is generally used with a List of Photos.