What is API?

If you’ve ever used an app to check the weather, signed into a website using your Google account, or paid for something online through PayPal, then you’ve already used an API - even if you didn’t realize it. An API is a part of the technology that works in the background and allows apps to talk to each other. In this blog, we’ll explain in simple words: what an API is, how it works, what types exist, and why they are so important.

What is an API?

API stands for Application Programming Interface. In the simplest terms, it’s a “middleman” between different programs. Imagine your computer is a restaurant, the user is a customer, the kitchen is the server, and the API is the waiter who takes the order and brings back the food. So, you (the app) don’t go directly into the kitchen (the server) - you communicate through the waiter (the API). The waiter knows how to pass the request and return the result.

Technically, an API is a set of rules and protocols. These rules define how two systems exchange information. For example, when your app asks for weather data, the API says: “Here’s what the request should look like, and here’s how the response will be structured.”

How does an API work?

An API works through a process made up of requests and responses. Here’s a simple example:

1. You open a weather app and enter your city.
2. The app sends a request to the server via the API.
3. The server processes the request and returns information.
4. The API then sends that information back to your app, and you see the forecast on your screen.

In other words, the API is the bridge that connects your app with data on the server. Without it, the app wouldn’t know how to "talk" to the server and would hit a dead end.

Types of APIs

There are several types of APIs, each with its own purpose:

• Open API (public) - this type of API is freely available to everyone. Think of it like a free pass: anyone can use it without special permission. For example, some websites provide a weather forecast API that anyone can use to show temperature and conditions in their app.
• Private API - used only within a specific organization or company. It’s like a private communication line. For example, a bank might have an API that connects its internal systems - but no one outside the bank can access it.
• Partner API - shared only with selected partners, not with the public. For instance, an online store might give partners access to an API so they can track stock levels in real time. It’s like a special key that only certain people receive.
• Composite API - designed to combine multiple different requests into one. Instead of having an app send three separate requests to the server, the Composite API packs them into one, making communication faster and reducing wait time.

Types of Communication

APIs can use different methods to communicate between systems. Here are the most common:

• REST API - currently the most popular. It works over the internet using standard methods like GET (get data), POST (send data), and so on. It’s fast and simple.
• SOAP API - an older type. It’s still used in large systems like banks and insurance companies because it’s stable and secure, though more complex.
• GraphQL - a newer approach. It offers more flexibility because the user can request exactly the data they need instead of getting the whole set of information.

Example (movies):

• REST: When you open an app, you see a list of movies - titles, posters, maybe a short description. That’s because the app sent a simple request like “give me popular movies,” and the REST API responded with a typical package of information. Quick and clear.
• SOAP: Asks for the same info, but through very strict rules. Think of it like filling out a detailed form: every field must be there and named exactly (like “Title”, “Year”, “Duration”). If something is missing or out of order, the request fails.
• GraphQL: Here, you choose what you want. You can say, “just send me the title and rating,” without images or descriptions. The advantage is you get only what you need, so the app loads faster and uses less data.

Benefits of Using APIs

Why are APIs so widely used? Here are a few reasons:

• Integration - APIs connect different systems that otherwise couldn’t work together. For example, a taxi app uses the Google Maps API to show the driver where to go.
• Saves time and resources - developers don’t have to build everything from scratch. If they want payment options, they simply use the PayPal API.
• Flexibility - APIs allow new features to be added easily without redesigning the whole app.
• Scalability - as the app grows, APIs make it easier to add new services.

One of the best examples is the Google Maps API. Thanks to it, apps all over the world can display maps and locations - without needing to build their own navigation system.

API in Everyday Life

You may not notice it, but APIs are almost everywhere:

• Weather apps - when you open a weather app, it uses a Weather API to show the data.
• Logging in - when you choose "Log in with Google/Facebook,” an Authentication API is working in the background.
• Online shopping - when you pay with your card or PayPal, the app uses a Payment API.
• Social media - when an app shows your Instagram feed, it uses the Instagram API.

The API is like an invisible network that connects all the digital services we use. Without it, most modern apps wouldn’t exist.

Security and Challenges

Even though APIs are powerful, they come with challenges:

• Authentication - it’s important to know exactly who is using the API to prevent abuse. This is usually done with special "keys" (API keys) that identify each user. A safer method is using systems like OAuth, which checks a user’s identity before granting access.
• Rate limiting - imagine someone tries to send hundreds of requests per second. The API could get overwhelmed or crash. That’s why there’s a limit on how often one user can send requests in a certain time. This helps protect the system from abuse and keeps it stable.
• Documentation - for developers to use an API, they need to know exactly how it works: what data it takes, what it returns, and how to use it. That’s why clear and detailed documentation is essential. Without it, using the API becomes confusing and difficult.
• Security risks - if an API isn’t well protected, hackers could get access to private data or disrupt the app’s functions. So protection is always important: using encryption, verifying users, and monitoring suspicious activity.

Conclusion

The API is a pillar of the modern digital world. It’s the bridge between apps and data, allowing systems to communicate without problems. Thanks to APIs, we can now use complex apps without having to think about how they work behind the scenes.

Next time you open an app to check the weather, order food, or log in through a social network, remember - there’s an API working behind the scenes making it all possible. It’s the “invisible engine” that powers most of the digital experiences we take for granted today.