You can use logic to control fields on a form, calculate prices, auto-populate, etc. Some common ways logic is used is to provide discounts to registrants who enter a code or revealing/showing an option or question to purchase membership if the non-member option is selected.
Picture below taken from the ePly system - Build a Form
Enabled - The field is visible and will only be selectable/editable if the correct dependent value is selected. If it is not selected, the field is visible but greyed out, making it unavailable to be selected/editable.
Derived Value - A value taken from another field to automatically populate the field this logic applied to. For example, if the company name is the same for both the primary registrant and their guest registrant, you can apply the derived value logic in the company name of the guest registrant, so that there is less repetitive typing.
Pricing - Changes the price of the section. This is especially useful when applying discount codes. See Set Up Fixed Amount Discounts
Disabled - The field is visible and will not be selectable/editable if the correct dependent value is selected. If it is selected, the field is visible and will remain selectable/editable.
Show - The field will appear on the form if the correct dependent value is selected. If it is not selected, the field will remain invisible.
Hide - The field will disappear on the form if the correct dependent value is selected. If it is not selected, the field will remain visible.
To see and experiment how each logic type functions, please visit our "All About Logic" testing form.