DefaultBy default, exclusive_categories is turned off. Turning off this option allows the user to select more than one category at a time and as a result all events satisfying either category (OR) will be shown.
In the example below I have selected both "Academic Calendar" and "Important Dates" (noted by the red arrows). By choosing both of these category options, any event that is in either of these categories will be displayed.
Turning on Exclusive CategoriesTurning on "exclusive_categories" allows the user to only select one category at a time. An "All" link will also appear at the top of the menu letting users display all events. This is useful when using categories as a navigation
<widget type="events_calendar"> <arg id="exclusive_categories">true</arg> </widget>
Result: Users can only select one category at a time for filtering events and an "All" link is displayed (see red arrows)