Written by Sümeyye Sever (notes I took while creating web development projects)

An API, which stands for application programming interface, is a set of protocols that enable different software components to communicate and transfer data. Developers use APIs to bridge the gaps between small, discrete chunks of code in order to create applications that are powerful, resilient, secure and able to meet user needs. Even though you can't see them, APIs are everywhere—working continuously in the background to power the digital experiences that are essential to our modern lives.

For example:

• A weather app on your phone uses an API to fetch current weather data from a remote server.
• An e-commerce website uses a payment gateway API to process payments.

How do APIs work?

APIs work by sharing data between applications, systems and devices. This happens through a request and response cycle. The request is sent to the API, which retrieves the data and returns it to the user. Here's a high-level overview of how that process works.

1. API client

The API client is responsible for starting the conversation by sending the request to the API server. The request can be triggered in many ways. For instance, a user might initiate an API request by entering a search term or clicking a button. API requests may also be triggered by external events, such as a notification from another application.

2. API request

An API request will look and behave differently depending on the type of API, but it will typically include the following components:

• Endpoint: An API endpoint is a dedicated URL that provides access to a specific resource. For instance, the /articles endpoint in a blogging app would include the logic for processing all requests that are related to articles.
• Method: The request's method indicates the type of operation the client would like to perform on a given resource. REST APIs are accessible through standard HTTP methods, which perform common actions like retrieving, creating, updating, and deleting data.
• Parameters: Parameters are the variables that are passed to an API endpoint to provide specific instructions for the API to process. These parameters can be included in the API request as part of the URL, in the query string, or in the request body. For example, the /articles endpoint of a blogging API might accept a “topic” parameter, which it would use to access and return articles on a specific topic.
• Request headers: Request headers are key-value pairs that provide extra details about the request, such as its content type or authentication credentials.
• Request body: The body is the main part of the request, and it includes the actual data that is required to create, update, or delete a resource. For instance, if you were creating a new article in a blogging app, the request body would likely include the article's content, title, and author.

Example API Request: Creating a New Article

Endpoint:

https://api.example.com/articles