Tags are great organizational tools and can be used in many different ways. We mainly use them to track different project phases, tasks, and sub-projects.
Tag Lists allow you to standardize your timesheet reporting. They can be used to track the phases and activities of a project:
You can add multiple tag lists to a project but keep in mind that you can only apply one tag per list to an entry.
Each tag list is comprised of individual tags that allow you to track the granular detail of what you work on within a specific project phase or task.
They're a really simple way of drilling further down to see how users spend their time:
Remember that only one tag from a tag list can be selected per entry.
Note: Deleting a Tag List in Settings > Tags will remove the Tag List and included tags from any associated entries.