When a Visualforce form submission component specifies a rerender attribute, this causes a partial refresh of the page to take place, redrawing the specified components based on the result of the submission. This can be used to change the elements on the page based on the user input; for example, to guide the user through creating a record of a few fields at a time.
In this recipe, we will create a Visualforce page that allows the user to create an account record. If the user chooses an account type containing the word customer, additional fields will be rendered to capture additional customer-specific information.
This recipe makes use of a controller extension, so this needs to be present before the Visualforce page can be created.