In Juju, a script refers to any script you execute on a compute resource provisioned by Juju, whether it is a charm action or another kind of script, e.g., a terminal command.

Script tasks

In Juju, a task is the execution of a script on a target unit (e.g., for actions, via juju run, or, for other arbitrary scripts, via juju exec).

Action tasks are run as defined by the charm author (default: sequentially), whereas tasks related to other scripts are run as set by the charm user (default: parallel).

A group of tasks queued by running an action across one or more units forms an operation.

Script operation

In Juju, an operation is the group of tasks queued by running a script across one or more units.