Selenium is an open source, automated tool used to test web applications across various web browsers.

Selenium is used widely as a testing tool for the following reasons:

Selenium is is easy to use as it is primarily developed in JavaScript.

It can test all web applications against various we browsers like Firefox, Chrome, Opera, Microsoft Edge, etc..

Tests can be coded in several programming languages like Python, JAVA, Ruby, Perl..

One of the main uniqueness of Selenium is - It is platform Independent, meaning it can deploy on Windows, Linux, etc..

It can also be integrated with other tools like Junit and TestNG for test management.

Selenium has a dedicated suite that facilitates easy testing of web applications.

Components of Selenium

Advantages of Selenium testing:

1. Selenium has proven to be accurate with results and thus making it extremely reliable.

2. Since it is an Open - Source, anyone willing to learn testing can begin at no cost.

3. It supports a broad spectrum of programming languages like python, PHP, JAVA, etc..

4. Selenium has plenty of re-usability and add-ons.