What is an API (Application Programming Interface)?

API (Application Programming Interface) is a set of rules and protocols that define how different software components can interact with each other. The API determines which functions, methods, and data may be available for use in the program code of one application from the other. The API can be implemented as a set of libraries, classes, functions, or web services that are provided to developers to interact with other applications or services. They determine which requests can be fulfilled, which data can be transmitted and which responses are returned. The API is used to create an interface link between different software components, allowing them to share data and perform interaction. For example, web services often provide an API that allows other applications or services to query them and obtain results, making integration and interaction with those services easier. The API can also be used to develop extensions, plugins, or applications, allowing developers to use the functionality of the underlying software. Using the API allows you to expand the functionality of the program by using ready-made components instead of writing all the code from scratch. The API is an important element of modern programming, as it allows you to build complex systems, distribute tasks between different components and promotes the rapid development of software.

To better understand the API (Application Programming Interface), you can use a real-life analogy. Imagine that you are in a restaurant and ordering a dish. In this context, a restaurant can be considered as a service or system, and an API - as an interface for interaction with this system. To order a dish, you do not need to know all the details about the cooking process. Instead, you use a menu that is an interface to available dishes. The restaurant menu indicates the names of dishes, their components, possible options and prices. This is information that is available to the customer and you can choose what you need. When you place an order, chefs use your order, its details and specifications to prepare the dish. In this analogy, the API is the restaurant menu. It defines the available options, allows you to choose what you need. You can place an order, and the restaurant can fulfill it according to your specifications and return the finished dish to you (answer). There are other variants of this analogy, where the API is the waiter who takes the order, passes it to the kitchen (server) and returns the answer (the finished dish, or the error - the ingredients are out, etc.). Thus, the API helps to provide convenient interoperability between two separate systems where one party (the client) can use the functionality and services of the other party (the system) through a defined interface.