Selenium WebDriver Architecture

 It consists of Selenium IDE, Selenium RC, Selenium WebDriver and Selenium Grid.

Selenium IDE:
Selenium IDE (Integrated Development Environment) is a Firefox & Chrome plugin. It allows us to record and playback the scripts.

Selenium RC:
It is basically a HTTP Proxy Server which injects JavaScript into a browser to automate the actions.

Selenium WebDriver:
Selenium WebDriver is a browser automation framework that accepts commands and sends them to a browser. It is implemented through a browser-specific driver. It controls the browser by directly communicating with it.
Selenium WebDriver supports Java, C#, PHP, Python, Perl, Ruby. Operation System Windows, Mac OS, Linux, Solaris. Browsers Mozilla Firefox, Internet Explorer, Microsoft Edge, Google Chrome, Safari, Opera Android, iOS, HtmlUnit.

Selenium Grid:
It is a Selenium API which can be used to run automation tests on multiple browsers and operating systems.

The Selenium WebDriver Architecture follows the popular Client-Server architecture and consists mainly of four components:

• Selenium Client and Language Bindings
• JSON Wire Protocol over HTTP
• Browser Drivers
• Web Browsers