An agreed interface that lets one piece of software talk to another — your app to your server, or your product to a third-party service such as payments or maps.
Almost every modern product is a set of APIs talking to each other. A clean, documented API is what lets you add a mobile app, a partner integration, or a new payment provider without rebuilding the core.
We design APIs contract-first, version them from day one, and document them so frontend, mobile, and third parties can work in parallel. Authentication, rate limits, and error formats are agreed before the first endpoint ships.