There are many reasons that Selenium be selected as a test tool:-
1. Selenium is a pure and open-source, freeware and portable tool.
2. It supports a variety of languages that include Java, Perl, Python, C#, Ruby, Groovy, JavaScript, and VB Script. etc.
3. There are many operating systems which is being supported by Selenium like Windows, Macintosh, Linux, Unix etc.
4. Browsers like Internet Explorer, Chrome, Firefox, Opera, Safari etc are being supported by Selenium.
5. You can integrate it with ANT or Maven kind of framework for source code compilation.
6. You can easily integrate Selenium with TestNG testing framework for testing our applications and generating reports.
9. It can be used for Android, iPhone, Blackberry etc. based application testing.
10. Selenium requires very less CPU and RAM consumption for script execution.
11. Selenium comes with the different component to provide support to its parent which is Selenium IDE, Selenium Grid and Selenium Remote Control (RC).
If you like reading you must read the following Selenium Tutorial. You can also watch the following Selenium video tutorial to learn it better. .
To learn in-depth about Selenium, sign up for an industry based Selenium course.