After you have completed your timesheet as a Tempo User, you can submit the timesheet to a Reviewer. Certain other people can also submit your timesheets for you. By default, your Team Lead can do this. Once you have submitted your timesheet for approval, you no longer can create or edit worklogs in the submitted period.
If you are a Reviewer, you can use the approval page to either approve or reject timesheets submitted to you. The Requester will be notified by email once their timesheet is approved or rejected.
You can manage timesheet approvals for your team by viewing the timesheets of your team members, reviewing past actions in the Approval Log, or adding a grace period for a specific team member.