The purpose of the transaction and transaction group is that the users can find quickly the observation.
For example I have some observations about the nutrition of patients. In my hospital all this observations is agruped with same transaction group: Dietitian Questionnarie. And every time that one patient do this questionnaire, is a different transaction.
Another example is a transaction group named: Vital Signs that containe some observations:
Systolic Arterial Tension
Tension Arterial Mitja
Diastolic Arterial Tension
Each time that the partiotioner mesaure any observation of this group represent a transaction.