What Is an API?
When you use an app on your phone to check the weather, your phone doesn't actually measure temperature. Instead, it asks a weather service for that information. The way it asks — and the way the service responds — follows specific rules. That's what an API is: a defined way for software to communicate with other software.
API stands for Application Programming Interface. Think of it as a contract between two systems. One system says, "If you ask me in this specific format, I'll respond in this specific format." This predictability makes it possible for completely different programs to work together.
How APIs Work
APIs work through endpoints — specific addresses where you can send requests. Each endpoint handles a particular type of request. For example, a weather API might have one endpoint for current conditions and another for forecasts.
When you make a request, you typically include:
- The endpoint URL — where to send the request
- The method — what action you want (like "get data" or "send data")
- Parameters — specific details about what you need
The API processes your request and sends back a response, usually containing the data you asked for or a message about what happened.
The Restaurant Menu Analogy
Imagine a restaurant. You don't walk into the kitchen and cook your own food. Instead, you look at a menu, choose items, and tell the waiter what you want. The kitchen prepares your order and the waiter brings it back.
The menu is like API documentation — it tells you what's available and how to order it. The waiter is like the API itself — the interface between you and the kitchen. You don't need to know how the kitchen works; you just need to know how to order.
Why APIs Matter
APIs are everywhere in modern software. When you log into a website using your Google account, that website uses Google's API. When an app shows a map, it's probably using a mapping API. When you pay online, payment APIs handle the transaction.
For developers, APIs mean you don't have to build everything from scratch. Need to send emails? Use an email API. Need to process payments? Use a payment API. This lets you focus on what makes your application unique.