Selenium: Class 1005 (Selenium-WebDriver A.K.A Selenium 2.0)
Client Version: 2.42
Java based Selenium Web Driver: Url: http://selenium.googlecode.com/git/docs/api/java/index.html
The Selenium Web driver JAR file size user needs to download is 23.6 MB.
And after download this external .jar they need to add them in Eclipse IDE external JAR location.
Its same as adding Android SDK or any other external libraries in the eclipse ide. Don't worry if you don't know how to add external .jar files in ide.
I will soon share a CBT on youtube channel, so follow the same and you are able to do it in quick time :)
Here is the screen-shot of extracted / unzipped selenium web driver .jar.