API is the acronym for Application Programming Interface. According to the definition on Wikipedia, an API specifies a set of functions that accomplishes specific tasks or allows working with specific software components. As web applications grow larger, we might need to provide the application services or data to third-party applications. We cannot let third-party applications access our source code or database directly due to security reasons. So, APIs allow the access of data and services of the application through a restricted interface, where users can only access the data provided through the API. Typically, users are requested to authenticate themselves by providing usernames and necessary passwords or API keys. So, let's look at the advantages of having an application-specific API.