Categories are questions where you can connect up to three queries with different alternatives. E.g. if you want to point out a certain room in a hotel consisting of more than one building, you can have the queries Building, Floor and Room (to select a room number). In this case you start by creating alternatives for Building. Under each building alternative you create the next query Floor where you add the different floors that exist in the current building. If you want to add another query, Room, you highlight each floor and add alternatives for room numbers.