The summary feature (also called “review before submit”) is a handy feature that allows your users to review the entered data before submitting.
This feature makes multi-paged forms even more powerful. A summary field can be added in order to review the form entry before it is submitted. It shows the submitted content of all form fields that have been filled out so far, so it can be used as a last verfication step: the visitor sees what he or she has entered into the form, be it personal data for a job application, or a list if the chosen products before submitting or moving on to payment.
I don’t see these very often, but when I do, I’m impressed. If you consider leveling up your on-site customer service, then the summary feature is for you.