The best way to illustrate this, I suspect, is to share my own story.
My daughter went through a stage where she loved the Disney princesses, as she called them. When we finally made it to Disney World in Orlando, we made a point to try to get a picture of our daughter with each and every princess. These were priceless.
Upon returning home, I thought my little princess might like a snapbook of these pics. So, I logged into Shutterfly, visited the store, and quickly put it together. In a few days, I had a nice snapbook, which she kept at her bedside for weeks.
There are an infinite number of themes that one could use to create a snapbook, whether it be a trip, organization, or whatever. And, snapbooks make great gifts.