My apologies that the Photos section of the site is so confusing! I won't begin to tell everyone how long it took for me to figure it out.
And thanks to Hutch for his explanation.
Here's how I understand everything, in case this helps...
There are 2 CATEGORIES of photos on the site, User Galleries and Sunline Floor Plans. Only I can add to the floor plans CATEGORY. Each user (also called a member) can create their own GALLERY in the User Galleries CATEGORY. And a user's GALLERY can be made up of 1 or more ALBUMS.
So if you visit the Photos page, you'll first see the CATEGORIES at the top of the page. And in each CATEGORY you will see GALLERIES, which are made up of 1 or more ALBUMS. The Random Files are Last Additions are a selection of files (photos) the program itself chooses for display.
Hope that helps!
Sarah