Here are some definitions useful in Agile processes.
Definition of TASK
An entry on a to-do list. Sometimes called a story, task, ticket, defect, bug, line item, or post-it.
Definition of READY:
When the task can be worked on.
It’s ready when there’s nothing preventing work from starting.
Definition of DONE
When there’s nothing left to do.
As strange as that may sound, and as facetious is it may appear, this is the underlying truth that is missed by many. Add as many criteria as you need to help you understand when the work has been completed, but it’s only truly done when there is literally nothing remaining.
Definition of WORK
Anything that advances the task beyond initial idea
This includes design, code, testing, annotations and documentation, or creating more to-do entries.
Again, this may come across as facetious. However if it takes effort it is work and should be counted as such.
Definition of IDEA
Something that can be done.
Definition of GOOD IDEA
Something that can be done with tangible and measurable benefits. Only good ideas should be worked on, ideally in order of most benefit.