A combo room is a room that can be divided into two or more smaller components. This is typically done with an air wall or some other kind of moveable divider
It makes it easy to quickly check space availability. With a combo room the system is aware of the relationship between the larger space and it's smaller components. If one of the smaller components is in use then the larger space will not be available. Likewise if the larger space is in use none of the smaller components will be available.
For example imagine you have a room called Grand Ballroom. The room has the following 3 components.
Ballroom A, Ballroom B and Ballroom C
These are the components that make up the Grand Ballroom. You may also choose to define other combinations such as Ballroom AB with the components of Ballroom A and Ballroom B
If Ballroom A is in use then the Grand Ballroom and Ballroom AB will not be available.
To define a combo room you must first define the components that make up the larger room. In this example you would define Ballroom A then Ballroom B and finally Ballroom C before defining the Grand Ballroom and any smaller combinations such as Ballroom AB.