The slideshow displays each image and its details, in turn and in the order that it appears, from either the ‘view results’ or the ‘pasteboard’ screen. The highlighted word underneath ‘slideshow’ on the navigational bar indicates where you started the slideshow from.
If you are viewing only the selected images in ‘view results’ then the slideshow will be limited to just these.
The show can be paused at any time by clicking on the stop button, or you can navigate forwards or backwards through the selection by using the forward and reverse buttons; this alters the direction in which the show plays through the set of images. When the show is paused, you can also download or order that image.