A form comprises multiple tables. Each table can have a different number of columns and rows.
These tables come in 3 different varieties.
A normal table just has a fixed number of rows and columns, and usually these tables comprise the bulk of the form.
A list table is one where a list of items is represented, one item per row. Users can add or remove rows.
A checklist table also represents a list of items, but its usually a list of items to be completed against a checklist.
The checklist itself is maintained by the Administrator, so it can change over time.