In this chapter, you will learn about a C and Objective-C language feature called blocks. A block is a set of instructions. It is an object, but it is called like a function. Blocks provide conveniences for a programmer and performance boosts for applications. If you are familiar with other high-level languages, you may know blocks as closures or anonymous functions. This chapter will introduce blocks and their syntax. In the next chapter, you will put blocks to use in your Nerdfeed application.