Note this additional state results are not available if you are using Replicate in your Activity.
The Activity is ready to process work, but there are no work items in any objects that feed it waiting to be processed.
The Activity is processing Work Items.
The Activity has completed processing the Work Item but the objects it routes out to don't have any capacity to accept the completed Work Item. Therefore, the Work Item must stay in this Activity and the Activity is blocked from accepting any new work.
The Activity has efficiency settings that mean the Activity is broken down and no work can be processed until it is repaired.
When a Activity starts processing a different type of work, it can be set up to do a change over. This is extra time the Activity must spend setting up to be able to process the work. Change over records the amount of time the Activity has spent setting up.
Activities can have their availability constrained to certain times of the day using shifts. This records the amount of time the Activity has been unavailable to process work because it has not been available due to a shift constraint.
The Activity is available to process work, there is work waiting in a feeding object for it to process, but there are no Resources available for it to use.