APIs, or application programming interfaces, are the gateways to the digital world. They link a wide array of software applications and systems. APIs facilitate communication between different software systems, and so power everything from social media — think of the share buttons on webpages — to ecommerce transactions.
At a simple level, APIs are like electrical sockets. A software application that you’re using, say the playback controls for a video on a webpage, is like an appliance. The system that provides data or services that the application needs, say YouTube, is like the electrical grid. The API, in this example the YouTube Player API, is like the standard electrical outlet that lets any appliance plug in to the grid.
APIs are not really so simple, though. Another analogy is a restaurant. The customer is the software application, the chef is the data or service, and the waiter is the API. The waiter brings the customer the menu, which lists available dishes — i.e., options for accessing data or service — and then brings the customer’s request to the chef.
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