There are two types of site categories: inclusive or exclusive.
Inclusive site categories include all of the configurable properties in the system by default. Because all properties are included, you must specifically exclude properties that you do not want appearing in the site category.
It is best to specifically exclude all configurable properties that are not required for the type of site that the site category supports. The default site category shipped with Site Administration is inclusive, but can be modified to exclude specific properties.
Exclusive site categories exclude all of the configurable properties in the system by default. With an exclusive site category, you must specifically include all configurable properties that are required for the type of site that the site category is required to support.
Exclusive site categories can append or ignore new configurable properties:
Append New Properties - When a new configurable property is added to the system, it is automatically added to the site category and available to the site administrator to set as part of the site process.
Ignore New Properties - When a new configurable property is added to the system, it is not automatically added to the site category. The new configurable property is only available to the site category if specifically included.
Important: It is best to avoid setting default values for site properties at the repository level. When a property is excluded from a site category, no value for that property will be included in your site configurations based on the site category. If, however, a default value for a property has been set at the repository level, then the value will be included in the site configuration even though the property may have been excluded from the site category.
