What is Visualforce?
Visualforce is a framework that allows developers to build sophisticated, custom user interfaces that can be hosted natively on the Force.com platform. The Visualforce framework includes a tag-based markup language, similar to HTML.
In the Visualforce markup language, each Visualforce tag corresponds to a fine-grained user interface component, such as a section of a page, a related list, or a field. The behavior of Visualforce components can either be controlled by the same logic that is used in standard Salesforce pages, or developers can associate their own logic with a controller class written
Where Can Visualforce Pages Be Used?
Developers can use Visualforce pages to:
• Override standard buttons, such as the New button for accounts, or the Save button for contacts
• Override tab overview pages, such as the Accounts tab home page
• Define custom tabs
• Embed components in detail page layouts
• Create dashboard components or custom help pages
• Customize, extend, or integrate the sidebars in the Salesforce console (custom console components)