Deactivation of an employee is useful if they are no longer available in the company for a longer period of time, e.g. due to parental leave. Now, this employee will not be able to log into their account until they are reactivated. They are no longer displayed in the employee overview of the calendar and therefore an accidental assignment to shifts is no longer an issue.
How it works:
Click on the employee symbol (red tie) on the left-hand side in the menu bar → click on the name of the desired employee → "Employee data" tab → click on "Deactivate employee"
The deactivated employee can still be seen in the employee overview. You can recognize deactivated employees by their grayish names and the label "Inactive".
Of course, the employee can be reactivated at any time (to do so, repeat the steps as above and click on "Activate employee").
Deactivated employees are still counted in the license fees, regardless of their status. If you want to add new employees, you have to delete the employees or upgrade your package.