A set of instructions that can react on the user's interaction with Visualforce markup (for example, a button click or a link click) is called as a controller. A controller can control the behavior of a page and it can be used to access the data which should be displayed on the page.
This chapter will introduce you to a few types of controllers and extensions that can be used for Visualforce pages. We will learn the types of controllers with examples.
This chapter covers the following topics: