What is an API? Simple explanation for entrepreneurs

What is an API and why do you need one?

API stands for Application Programming Interface. Simply put: an API is a standardized way for two systems to talk to each other. When you pay with Swish, an API is involved. When your website retrieves your Google Maps map, an API is involved. When ChatGPT enables a phone company to use AI, it is via an API.

A concrete analogue

Think of a restaurant. The kitchen is the database and the dishes are the data. The checkout is the user interface. The server is the API – the one that receives your order in a standardized format, communicates it to the kitchen, and delivers the response back to you. You don't need to know how the kitchen works; you only communicate via the servitor.

Why does your business need an API?

First, it enables integrations. Your CRM can automatically receive information from your webshop via API. Your financial software can retrieve orders from your platform via API. Without the API, someone has to do this manually.

Second, it enables scalability. When you open an API, a mobile app, a partner service, and your internal back-office can all use the same data source. You build functionality once and expose it via API.

Third, it enables AI. Virtually all AI services are consumed via API – OpenAI, Anthropic, Google Gemini. To use AI in your product or workflow, you need to understand how API calls work.

REST vs GraphQL – the two most common API types

REST (Representational State Transfer) is the dominant API standard. It is simple, well-known and understood by many tools and developers. When you call a REST API, you specify which resource you want (eg /users/123) and which you want to do (read, create, update, delete).

GraphQL is a newer option from Meta where the client itself specifies exactly which data fields it wants. It reduces the transfer of unnecessary data and is strong for complex data patterns, but has higher complexity and is overkill for simple use cases.

What is API security and why is it critical?

Unsecured APIs are one of the most common security risks for businesses. API keys must never be exposed in client code. Rate limiting ensures that an API cannot be overloaded by automated calls. Authentication via OAuth or JWT ensures that only authorized users and systems can call sensitive endpoints.