Application Programming Interface (API)

An application programming interface, or API, is a defined way for software systems to request information or trigger permitted actions. A cleaning company's website could use an API to send appointment details to a scheduling service instead of maintaining two separate calendars. The API specifies what information is accepted, how a request is made, and what comes back. It is not the same as a visual button or a complete integration: developers still need to connect the systems, handle errors, and protect credentials. APIs make certain connections possible, but their reliability and cost depend on the services involved.