This document discusses APIs (application programming interfaces) and their role in web development. It defines APIs as specifications that allow software components to communicate with each other. On the web, APIs typically use HTTP requests and JSON/XML responses to allow access to structured data and services. This has enabled the combination of multiple online services into new applications. As more websites provide APIs, the web itself is becoming a platform that outside developers can build upon. However, there are also limitations and ethical issues to consider regarding APIs, including restricted access, changing formats, and debates around scraping data versus using official APIs.