API的全称是应用编程接口（Application Programming Interface），这并不是一个新概念，在计算机操作系统出现的早期就已经存在了。在互联网时代，把网站的服务封装成一系列计算机易识别的数据接口开放出去，供第三方开发者使用，这种行为就叫做开放网站的API，与之对应的，所开放的API就被称作openAPI。Open API (often referred to as OpenAPI) is a word used to describe sets of technologies that enable websites to interact with each other by using SOAP， Javascript， and any other web technology. While its possibilities aren't limited to web-based applications， it's becoming an increasing trend in so-called Web 2.0 applications.