What is Selenium?
Selenium is a free open source-testing tool for Developers. It is known as automated testing tool for web applications. If you test software by selenium, it is called selenium testing. We should not consider selenium as one tool. It is the combination of multiple tools. 
Who is behind selenium?
As I mentioned it is a collection of different tools, it has few founders behind its creation. Now I will tell you about them.
Jason Huggins – The first person is Jason Huggins, he created selenium in 2004, worked as a engineer at thought works. He use to work on web applications that needed for frequent testing. He observed that they were using more manual testing for their applications. After that, he designed a JavaScript program that automatically manipulate actions of the browser. Finally, It was named as “JavaScriptTestRunner” , after that it made as open source for every one and named as selenium core.
Paul Hammant – After the invention of selenium core, it used frequently by testers. So, the testers who use it to install the total application. Therefore they have to install web server in local computers. To Reduce this process , paul hammant another software from thought works has designed server that act as HTTP proxy, Best Known as Selenium Remote control.
Patrick Light body – developed Selenium Grid to reduce the test execution process. It initially known as “Hosted QA”. It’s work is to get the browser photos in different stages. Best used for transferring commands to machines.
Shinya kasatani - Has developed selenium IDE, known as Firefox extension, automates browser by playback and record. It invented to increase the speed of designing test cases and given selenium IDE to selenium in 2006.
Simon Stewart – Designed Selenium web driver circa in 2006, during the time when browsers and applications. Became more restrictive by Java programs known as selenium core. It is the first platform-testing framework, which manipulates browser from OS level.
What is selenium 2
Specifically Selenium combined RC and web driver, for designing selenium 2. It developed, but now it is maintenance. Now every selenium project is focusing on selenium 2.
Now we will discuss little bit more about it.
In the mean while go through our Selenium online training video
https://www.youtube.com/watch?v=YJb21bvbpVMWe all know that it is a portable and easy framework, for testing web applications. As an illustration It offers playback tool for guiding functional test methods, without knowing more about test language. With the result we can do this test on latest web browsers.
Generally it is a simple tool, that which make use of simple scripts, to run tests with a browser. So, In Simple and easy terms it is known as selenium automate browser. Simultaneously this framework is portable for web applications that offer record/play back.
What is selenium client API?
It is an alternate for tests. Test scripts can written in many languages. So how this test scripts will communicate with selenium. In particular test scripts Interact by calling in selenium client API. At present it is offering clients APIs for Python, Java script, Ruby, C#.
Best steps for selenium testing
Design a Web driver example.
Direct to a web page.
Assign a HTML element on webpage.
Do an action on HTML element
Run multiple tests and make a note of test results, by test framework.
At last, finish the test.
Why only Selenium Tool is used?
First selenium software is free and it an open source. Even Facebook and Google uses it for testing their web applications. It will give perfect output when we test a software or a web application. At the same time, we again use this test script in Automation testing.
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To illustrate, it is a community based testing tool. For instance With this tool we can do tests on multiple web browsers. So, It has its own inbuilt language, a tester not limited to write a single language. Moreover it support by any language like python, PHP, Java script, Java and it is considered as best selenium benefits.
The best it has ,it can integrate with any other tool like Qmetry, Selenium grid, Saucelabs, Hudson and many more. Support web applications like AJAX and JavaScript.
I have given a brief Introduction, in our what is selenium blog. I think you enjoyed it. To know more about it, Go through our blogs. You can also refer our video tutorial given by a selenium tester.
Especially to make a good career with testing, go through our live online selenium 3.0-certification training. Onlineitguru is one of the best software training institutes
If you have any doubts, feel free to contact our selenium automation team.