Visualforce is a framework for building custom user interfaces for Salesforce data using a component-based tag syntax. It follows the model-view-controller pattern with standard and custom objects as the model, Apex code as the controller, and Visualforce pages as the view. Visualforce components have a prefix identifying their library and a name indicating their type, and attributes are used to pass values to the components. Over 140 standard Visualforce tags are available to create fields, actions, charts, and more, or custom components can be built by integrating Visualforce with HTML, JavaScript, and CSS. The presentation demonstrated building Visualforce pages.