APIs

The software intermediary: APIs (Application Programming Interfaces) define the rules for two applications to communicate, enabling secure data exchange and functionality access.

APIs are the essential contracts that allow distinct software systems to interact without exposing internal code. They operate on a request-response cycle: a client sends a structured request (often via HTTP methods like GET or POST) to a specific endpoint (URL), and the server delivers a formatted response (typically JSON or XML). Major architectural styles include REST (Representational State Transfer) and SOAP (Simple Object Access Protocol). This standardized protocol allows massive-scale integration: for example, a travel application uses the Google Maps API for location data, or a payment gateway API (like Stripe) to process a transaction securely. APIs accelerate development by leveraging existing services, drastically cutting time-to-market and development costs.

https://www.redhat.com/en/topics/integration/what-is-an-api