A system administrator has the right to make changes in the system settings of the organisation. The system administrator can also see temperature and comments of the whole organisation. Winningtemp is always protecting the anonymity of the user; it doesn't show any data that can be associated with any particular individual.
A group administrator is normally a group manager or department manager or similar. A group administrator can see the temperature and comments of the group or department that he/she is responsible for (when the required anonymity level is reached).