As a visitor whenever I fill out a form on the landing page, each value will be validated based on the settings made for each field.

e.g. If the single input field is set to required - then on submission a check is done to see if a value was entered or not. If no, then an error message will be displayed, and the form will not be submitted.

All the possible scenarios are listed in the Form Builder confluence page - https://doc.ez.no/display/PR/eZ+Form+Builder#eZFormBuilder-UserStory2-AsaVisitor,Iwanttosubmitaformwithvalidatedinformation