By default, all employees are able to give feedback to anyone in the system. To give feedback, you can go to the Employee's profile and select "Give Feedback" in the top right hand corner.
Feedback that an employee receives, will be in their feedback tab on their HelloTeam profile. This feedback is not anonymous, employees will see the name of the employee who gave it.
Visibility
Employees are only able to view the feedback that they have given or received. Depending on how the system administrators set up permissions, direct managers and managers infinite up the hierarchy may also be able to view the feedback their employees have received in their "My Team" tab.