Selenium WebDriver 

Selenium WebDriver is the successor of Selenium RC (Remote Control), which has been officially deprecated. Selenium WebDriver accepts commands using the JSON-Wire protocol (also called Client API) and sends them to a browser launched by the specific driver class (such as ChromeDriver, FirefoxDriver, or IEDriver). This is implemented through a browser-specific browser driver. It works with the following sequence:

1. The driver listens to the commands from Selenium 
2. It converts these commands into the browser's native API
3. The driver takes the result of native commands and sends the result back to Selenium:

We can use Selenium WebDriver to do the following:

• Create robust, browser-based regression automation
• Scale and distribute scripts across many browsers and platforms
• Create scripts in your favourite programming language

Selenium WebDriver offers a collection of language-specific bindings (client libraries) to drive a browser. WebDriver comes with a better set of APIs that meet the expectations of most developers by being similar to object-oriented programming in its implementation. WebDriver is being actively developed over a period of time, and you can see many advanced interactions with the web as well as mobile applications.

The Selenium Client API is a language-specific Selenium library that provides a consistent Selenium API in programming languages such as Java, C#, Python, Ruby, and JavaScript. These languages bindings let tests to launch a WebDriver session and communicate with the browser or Selenium Server.