The photo gallery page allows the user to upload photos to create a gallery complete with thumbnails and captions. Note that the "Portfolio (Rich Media)" page type contains the photo gallery functionality, in addition to text and video functionality.
Once created, there will be 3 tabbed sections within in the edit page:
Page Content - From this tab you can change the title that appears in the page and add photos to the gallery.
Navigation Link - This tab modifies the page's relationship to the navigation tree. As such, it will only be available if editing a page that is assigned to a tree. Note that if the page is related to multiple navigation trees, this tab may change depending on what tree you were in when you clicked the page edit button.
SEO - Short for "Search Engine Optimization", this tab contains extra fields to fine-tune your page so that search engines can more easily index it.