The ADAPTIVESPLITAREA component renders two content areas with a divider in between. The way the content areas are arranged depends on the size that is available. The two content areas are positioned as children of the component.

Let's assume, the component is used with horizontal orientation: 
In this case the first content area is rendered on the left, the second content area is rendered at the right. The width of the first area is determindes by its content, the width of the right area is streched to the available width.
If the screen space is not sufficient to render both areas in parallel, then the left area will be rendered only on user request - otherwise it is hidden. In addition, if the left area is rendered then it will be rendered on top of the right area.

You tpyically use the component in scenarios in which you have some navigation content on the left which should be shown for big screens - but which should be visible on request only if running on small screens.

In this description "left" and "right" are used for explaining the arrangement of the contained content areas. If setting attribute ORIENTATION to "vertical" then there is a "top" and "bottom" area, of course. 
