Visualforce provides the facility for delivering template-driven web pages and email messages. In addition, developers wishing to simply utilize a basic container and maintain more control over the lifecycle of the request may choose Visualforce pages. Finally, organizations that can’t use Apex code can’t use Lightning Components, but they can use Visualforce.
<aura:method> is used to define a method as part of a component’s API. This enables us to directly call a method in a component’s client-side controller instead of firing and handling a component event. Using simplifies the code needed for a parent component to call a method on a child component that it contains.