The task table, like any table, consists of table columns (fields) that can store data for each record. In particular, the task table has several fields which are supremely useful for nearly any record that could be used to track work in ServiceNow. Below are some of those fields, and a description of their purpose. These fields may or may not be shown on the form or the list of any task-extended table, but all of them exist on all tables that extend the Task [task] table.
Active is a Boolean field. This means that it stores a true/false value, and displays on the form as a check-box. This field is often controlled by a business rule. A business rule is a server-side script that runs in response to certain events on a record. In this case, the event that triggers the State field is usually what determines whether the Active field should be set to true or false. The Active field is a good general indicator as to whether a state is... well, active!
The Active field...