Which term best describes something that is created, has worked performed upon it, and is eventually moved to a state of closed?

A report is a data visualization and analysis tool, not an item upon which work is directly performed and closed.

A flow (or workflow) defines the sequence of activities for a process but is not the item itself that work is performed on and closed.

An event is a record of something that happened in the system, often triggering actions, but it is not the primary record type for trackable work that is performed and closed.

A 'task' is a foundational concept in ServiceNow, representing any unit of work that needs to be performed, tracked, and completed. These records, such as incidents, problems, or change requests, follow a lifecycle from being created, having work done, and eventually moving to a resolved or closed state.