A huge portion of the Internet’s data travels over HTTP/HTTPS through request-response cycles between clients and servers. Every time that you use a website, your browser sends requests to one or many servers requesting resources. Every image, meme, post, and video is requested by a client and sent in a response from a server.

Express is a powerful but flexible Javascript framework for creating web servers and APIs. It can be used for everything from simple static file servers to JSON APIs to full production servers.

In this lesson, you will be fixing a machine called Express Yourself in the browser. The machine is supposed to provide functionality for clients to interact with various Expressions: JavaScript objects each containing ids, names, and emojis. Currently, it looks nice, but nothing works since there is no server in place! You will be learning all the necessary skills to implement an API allowing clients to Create, Read, Update, and Delete Expressions. These four functionalities together are known as CRUD, and they form the backbone of many real-life APIs.