One of the main benefits of programming is we don’t work in isolation. We can import modules that contain code that we can use to help us write our own programs. We use online documentation like MDN and W3Schools to help us learn how to utilize aspects of a programming language. We use online forums like Stack Overflow and Google to find answers to specific problems. We even use other people like our classmates, TAs, and instructors to help figure out how to solve problems.

We can also use other people’s data in our applications. There are multiple ways of using other people’s data, or external data, in our applications. Over the course of the next two chapters, we will focus on using fetch() and JSON to request and use data.


When using a website, we mainly work with GUIs (Graphical User Interface) which contain buttons, forms, text boxes, etc. However, our program does not know how to use a GUI. Programs use APIs (Application Programming Interface) to communicate with other programs.

Consider the software you use on a daily basis, like Microsoft Word, Google Chrome, or a music streaming device like Spotify. When you open the software, a window pops up on your screen and is filled with text, buttons, search bars, scroll bars, etc. Usually, with a little trial and error, you can learn how to use the interface easily. This interface we use is called a Graphical User Interface, or GUI for short.

We interact with computers using various interfaces, either with a GUI or a CLI. However, an application does not know how to use a GUI, or a CLI, and needs its own interface to communicate with another application. An API is the interface that allows one application to communicate with another application.

An API is how one application communicates with another application. We will be making a request to an API in order to retrieve information we need for our application.