Recommended. This displays your images in embedded pop-up windows when you click on them, darkening your website in the background, instead of taking you to another window.
Settings
The settings for Lightbox Plus can be accessed via the Appearance > Lightbox Plus menu. You can change the style of the Lightbox Plus pop-up in the first panel, Lightbox Plus – General Settings. We recommend changing the style to “Black,” but you may find other styles more to your liking.
To test a different style, simply change the setting in the Lightbox Plus menu, then open up one of your pages with image links (i.e. a photo gallery) in a new tab or window, and click on the image. Each time you change the style in the Lightbox Plus menu, you will need to refresh the page with the image link.
For more information, see the plugin page(s):
http://wordpress.org/extend/plugins/lightbox-plus/