The following section defines what a Subform is in ActivityInfo.
In ActivityInfo, a Subform allows you to collect data which needs to monitored over a period of time, or will occur multiple times. Subforms allow to enter data for any reporting frequency you need while still giving you the flexibility of a Form.
Subforms are included within a parent Form.
Records for a Subform can be added for any of the period you define. For example if you want to have a Monthly Subform, you will need to add to your Subform with a Month field.
If data needs to be collected on an irregular basis, you can use a Repeating Subform to enter Records whenever needed.