Modules are self powered classes that will extend your site to be more powerful and add further features to it like a Photo Gallery and so on.
This module allows you to have your own shopping (e-commerce) website where you can sale your items in different categories, attach pictures, attachments and even digital goods to them. For the items dynamic form is used so you can customize the item's details too.
This module extends your site with user registration/my account dynamic forms allowing you to have guests register on your site. You can customize both forms with any custom fields you want.