Above the thumbnail display area you have a slider for adjusting the thumbnail size, a menu for selecting which image details you want to see and how they should be sorted, and three buttons for the layout of the image browser area. We are currently in the grid view--the middle button.
All of the controls in Photoshop Express have "hover help" or "tool tips" to tell you what the control does when you hold your cursor over it for a few seconds.

There is also a Help menu which leads you to a discussion forum and other help options.