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Templates determine the layout of (mosttimes repeating) elements in a site layout. These elements could be bloacks as found in the left and right columns, or the block formed by this single post.
Templates assume a module or XOOPS version they were developed and tested on, but most basic functionalities don't change or stay compatible. So, most templates run on most XOOPS versions.
However if some new functionality is added to a module, then some older templates may have to be modified to add these new possibilities. This is also the case for themes.
The newer XOOPS version supports beneath the left and right column also divisions for the center column as the center left, center center and center right columns for top and bottom in the centercolumn. To make use of these positions, many older themes have to be adapted.