Activities define the things that a building can do beyond the normal activities. Buildings are associated with activities and once the building is built the building can be used to trigger the activities.
Configuring New Activities
Activities are configured in an XML file. Use the sample XML file ActivityData.xml as your starting point. You can use any name for the activity data file as long as you place it in a Unity Resources folder (any folder in the asset directory named Resources).
If you wish to use different XML files you can set the names in the properties of the ActivityManager object. Note that the extension .xml is not included in the entry; it is however required for the filename.
For details about configuring activities see: The Activity Configuration File
A note on Activity Icons