Webnodes includes a number of server controls you can use. Some controls are designed for use in visit mode, but others are the controls behind the Webnodes edit UI that you can reuse in your own custom modules.
There are a number of visit controls that can help you create your webforms based website. You don't have to use them, as we like to offer total freedom for template development, but they give you a choice.
In some cases, for example for the forum and blog modules, they can save you a significant amount of time, as the functionality in the controls for those modules is not something you build yourself in an hour.
Most of the visit mode controls use templates, so you have full control over the look and feel of your application, even if you use controls that ship with Webnodes out of the box.
Most of the edit interface is built using a handful controls. You can use these controls in your own custom modules if you want.