the last project you opened will launch, or a blank project will launch, or a window will open asking you what you want to open.
new project - allows you to start a new project from scratch. you can import galleries and timelines from other projects into this project if you so desire.
load existing project - opens a browse window where you can search your system drives for the project you wish to work on.
most recent projects - click this and a drop-down menu shows you the projects that have most recently been saved on the system.