Visualforce is a component-based user interface (UI) framework that enables the creation of dynamic, reusable interfaces.

The Visualforce framework is part of Salesforce's Platform as a Service (PaaS) offering, which is designed to simplify the development and deployment of cloud applications and websites.

Developers define pages through specifying Visualforce markup and a Visualforce controller. The Visualforce tag-based markup language looks and behaves similarly to HTML. The markup embeds tags and web-enabled languages like HTML and JavaScript within a single <apex:page> tag. The Visualforce markup controls what elements appear on the page and how they appear. Visualforce tags correspond to page elements, such as form fields or and images. 

Controllers consist of instructions that specify what happens when users interact with page components, such as when a user clicks a button. Page components can be controlled by the standard logic for Salesforce pages, or developers can associate their own logic with a controller class. Server-side standard controllers simplify basic database operations, such as queries and updates.

See an introduction to Visualforce:

This was last updated in February 2016

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