The K2 component contains additional views: speakers and event. These layouts can be used for displaying speakers (the speakers layout) and other things like schedule, sponsors (the event layout).
You can specify the layout during creation of the category:
For the normal K2 pages please use the default layout as above, for the other pages you can select the speakers or event layout:
Please remember that the event layout contains the override only for the item.php file, so please don't use it for categories which will contain the regular category pages.