Advanced form rules and checks based on calculations of user input.
We would like to prevent "garbage in" as much as possible by adding constraints on webforms.
A good example would be for a Date of Birth field to only accept dates greater than 18 years ago.
Another example would be to say field [x] must be greater than field [y].
Joshua Jobin commented
Another great example would be "Hide Section 2 IF( FieldA + FieldB > 100)". Or simply allow a rule to be created from a calculated field.