How does a WebDriver work?

Selenium WebDriver is a set of open-source APIs that allows users to interact with any existing web browser and subsequently automate user operations within that browser.

The following processes occur in the background when a user writes WebDriver code in Selenium and runs it:

• An HTTP request is sent to the appropriate browser driver (Chrome, IE, Firefox). Each Selenium command has a specific request associated with it.
• The request is delivered to the browser driver by an HTTP server.
• The HTTP server decides whatever commands or actions the browser must carry out.
• The instructions/steps are carried out by the browser as previously decided.
• The automation script then displays the outcome after the HTTP server receives the execution status and delivers it back to it (as passed or as an exception or error).