application programming interface

a set of protocols and tools that allows different software applications to communicate with each other

Developers use the Twitter API to integrate Twitter functionality into their applications, such as displaying tweets or posting updates.
The Google Maps API allows developers to embed maps and location-based services into their websites or mobile apps.
The Spotify API enables developers to access music streaming services and create custom music applications.
The Facebook Graph API provides access to Facebook's social graph, allowing developers to retrieve user data and interact with the platform.
The RESTful API for a weather service allows developers to retrieve current weather data and forecasts for specific locations.