The multipage element allows you to create moving sections within a page design and make the most of screen real estate. In other words it is an element that can contains multiple pages which can slide or fade out. You can use as many multipage elements on a page design as you wish.
A multipage element will usually contain more than 1 page within it and there is no limit to the amount of pages you can have on a multipage.
If there is only one page on a multipage element it will remain static on the page, movement occurs when more than 1 page is added and a slide/fade animation is set to each page.
For more information please refer to section 6.3 (page 32) of your Optymyse userguide