A unique feature to The Sims 2: Bon Voyage are special memories called Vacation Mementos. They are displayed in a panel accessed from the Memories panel, and there are 45 of them to collect. Before they are unlocked, only the outlines of them are visible, but by hovering over them with your mouse cursor, a cryptic description is shown. When a Memento is unlocked, the relevant icon will become visible and an explanation of the Memento can be viewed by hovering over it like before.
As a Sim collects more and more mementos, the progress bar at the top of the Vacation Mementos window fills too. Next to that is the Sim's memento rank, which also increases as you gain more mementos. Finally, the suitcase icon gains more stickers as you get more too.