API

Web APIs commonly expose operations through HTTP endpoints and structured data. Browser APIs expose capabilities such as storage, graphics, location and network requests to JavaScript. In practical terms, API belongs to the browser, server or document layer. Knowing that layer is important because it tells you what the term can change, what it cannot change, and where to look when something behaves unexpectedly.

The common mistake is to use API as if it also meant AJAX. That blurs two separate decisions and usually sends troubleshooting in the wrong direction. A better test is practical: Inspect the endpoint contract: URL, method, authentication, request fields, response shape and failure codes.

In day-to-day work, API matters when one application needs structured access to another system. The practical value is not the vocabulary itself; it is being able to identify the right control, file, setting or decision when the concept becomes relevant.

A weather interface might request /api/forecast and receive structured JSON rather than an entire HTML page. That example is useful because it turns the definition into something you can recognize, test and discuss with other people working on the same project.

Use these references when you need documentation-level detail, specifications or product-specific behavior beyond the plain-English explanation above.