Themes offer you an easy way of changing the way your site is presented to the users of your site. Using themes, module pages can be changed in very fine detail to obtain the look you want.
Themes are built using Smarty templates, which separates the PHP logic from the module and the ImpressCMS core from the HTML codes that form the layout. That makes it easy to transform your standard HTML documents into a new layout for ImpressCMS.
Themes can be changed on the fly without needing calculations. That means you can have an adapted look-and-feel for your site for the Christmas season just by activating a new theme. After the Holiday period you just switch back and everything returns to normal.
Different user groups can have different themes, allowing you for example to have specific zones on pages for separate user groups.