https://www.w3.org/TR/webdriver2/#abstract
WebDriver is a remote control interface that enables introspection and control of user agents. It provides a platform- and language-neutral wire protocol as a way for out-of-process programs to remotely instruct the behavior of web browsers.
Provided is a set of interfaces to discover and manipulate DOM elements in web documents and to control the behavior of a user agent. It is primarily intended to allow web authors to write tests that automate a user agent from a separate controlling process, but may also be used in such a way as to allow in-browser scripts to control a — possibly separate — browser.
WebDriver 是一个远程控制接口，能够自我检查、控制用户代理。它提供一种平台和语言中立的有线协议，作为一种方式能够让进程外程序远程改变浏览器行为。
所提供的是一组接口，用于发现和操作网络文档中的 DOM 元素，并控制用户代理的行为。它的主要目的是允许网站作者编写测试，从一个单独的控制过程中自动化用户代理，但也可以用这种方式来允许浏览器内脚本控制——可能是单独的——浏览器。