Just as in traditional scrapbooking,
MemoryMixer uses layers. Each element of a page is on it's own layer and can be moved forward or backward by right clicking on an object. You an move them layer by layer or bring to the front or send to the back. If you have used a background, it will always be the bottom layer.
You can also use the layering short cut tools (my favorite) found along MemoryMixer's top tool bar. The first button will bring the selected item forward, the next button sends the item backwards, and the last button brings up the menu as shown above.
If you've ever had a photo box that you couldn't drop a photo into, it is because there are other elements positioned on top of the photo box. You can simply move those items backwards until the photo box is on top, add your photo and then send the photo box back. This feature allows you to have embellishments sit on top of your photo giving you total design control. This is the Nature Nut QuickMix that is found in MemoryMixer v3.
For more information check out this MemoryMIxer video on YouTube.