What is Selenium? Is it a WebDriver API or something else?
WebDriver is an official W3C standard for automating web browsers. It was created to help with cross-browser testing, as well as to facilitate automated browser interaction for use in web apps, mobile apps, and desktop applications. The WebDriver API—which is actually a suite of APIs, not just one—is the most common way for developers to create automated tests for their web applications.
Learn more: WebDriver | Selenium
Selenium is a complete web test automation tool and not a WebDriver. Rather it consists of four significant components namely:
Selenium IDE
Selenium RC
Selenium WebDriver
Selenium Grid
All these components are part of Selenium suite while Selenium WebDriver is a web framework that allows you to execute cross-browser testing. It allows automation of web-based app testing and choosing a relevant programming language for developing test scripts.