Web Application Programming Interface (API) Development
Web APIs are an instruction set of urls (like in your web browser) stating how to share data between two systems over the internet. The parties using it have to agree on the data model first (see data model section). Web APIs have become extremely popular because of their simplicity and usefulness. They can even carry a payload (see section on payload specification). There are two general categories of Web API: SOAP and REST.
An API can be written once and shared with others freely, making all systems using it compatible. Each new system using it just implements the API with their own code, and the API has enough instructions to achieve interoperability.