All users (including collaborators) on all account types can star tasks.
Starring tasks makes them easier to access in the future. When you star tasks, they appear in Starred tasks smart folder.
Starred items work on a person-by-person basis, which means everyone can select which items they want to favorite.
You can star a task from the Task view:
Open the task you want to star in Task view.
Click the star icon in the upper right-hand corner of the view.
The star icon turns blue and the task appears in Starred tasks smart folder. Click the star again if you want to remove the task from the starred section.
All the tasks you starred can be found in the Starred tasks smart folder in your Personal space.