A spread is basically 2 pages in your book that face one another. Think of your book laying open with page 1 to your left and page two to the right on the same physical piece of paper with the fold down the middle, your book will not start with one page on the right, it will start with a full spread. When you design a layflat book in the software you will work in spreads not pages. The spread of a layfalt book is mounted back to back to create 4 pages in your book or two separate spreads. When you design albums in the software you will work in spreads not pages.
Photo Books on the other hand work in pages. When you work in the software, you will design your book in pages not spreads. The first page of the book will be on the right side of the page with pages 2 & 3 following on the next open page.