Self-review allows an employee to assess his/her own progress and productivity. 

During a self-review, an employee evaluates his/her skills. This is an opportunity to find the gap between a manager's and an employees' assessments. 

How to activate a self-review option?

In All reviews list choose the Review you need. Click to "Edit Review".
To enable members to hold self-review, choose the Self-review on the Edit page.
 Select members who make self review. Then click to "Save changes".