The acronym "API" stands for Application Programming Interface. An API is a set of rules and protocols that allows different software applications to communicate with each other. It provides a way for developers to access specific functionalities or data from another service, application, or platform without needing to understand the underlying code. APIs are essential for enabling integrations, allowing disparate systems to work together seamlessly. They play a critical role in building web applications, facilitating features like user authentication, data retrieval, and more, enhancing overall functionality.