II. Selenium Tools.

Selenium

In 2004 Selenium came to the world of software. Mr.Jason Huggins who was working in ThoughtWorks company developed Javascript based record and playback script to speed up his web application manual testing task and he named this as Selenium IDE. And This javascript became core of selenium.

Later from Selenium IDE to Selenium RC. And Selenium RC was most powerful scripting tool during those days.

After that Simon Stewart engineer from Google started working on Webdriver now this also called "Selenium Webdriver"

"Selenium Tool" is also called as "Selenium Automation Suite" because "suit" means the package of many other tools.

Yes! Selenium Automation suit consists of many other tools and they are:

1. Selenium Integrated Development Environment (IDE).
2. Selenium Remote Control (RC).
3. Selenium WebDriver.
4. Selenium Grid.

I. Selenium Integrated Development Environment (IDE).

IDE - Means an integrated development environment. Is a software application that provides comprehensive facilities to computer programmers for software development.

From above IDE definition it's clear that using IDE we can develop any software. For example "Eclipse" is IDE.

Selenium IDE: Selenium IDE has a recording and playback feature, which records user actions as they are performed and then exports them as a reusable script in one of many programming languages that can be later executed.

Advantages of Selenium IDE: Very simple to automate web application because it's just record and playback. No need to write any code in Selenium IDE. The code is generated automatically by IDE as when you start recording tests.

Disadvantages of Selenium IDE: It is not designed to run your test passes nor is it designed to build all the automated tests you will need. Specifically, Selenium IDE doesn’t provide iteration or conditional statements for test scripts. 

II. Selenium Remote Control (RC).

Selenium RC was the main Selenium project for a long time, before the WebDriver.WebDriver is also called Selenium WebDriver .Releases of WebDriver are  Selenium1 and Selenium2.

Selenium 1 is still actively supported (mostly in maintenance mode) and provides some features of RC

Selenium RC involves "Remote Control" Server need to be started for automating any web application. RC is behaving as a middle layer which takes all commands from user-written code and interprets and communicate with the web application.

 From Above diagram it's clear that Code is written in eclipse which communicates with RC server then RC interacts with the web application for intended operation.

III. Selenium WebDriver.

In the world of Automation implementation of Selenium Webdriver is the biggest change. In the market its also know as "Webdriver / Selenium Webdriver"

Latest version of Selenium webdriver is "Webdriver 3.0"  released in October 2016.

But in this tutorial, we will work on Selenium Webdriver 2.0 as its more stable than the 3.0.

Note: Advantage of Selenium Webdriver over RC is no concept of a Server here.

IV. Selenium Grid.

Selenium-Grid allows you run your tests on different machines against different browsers in parallel. That is, running multiple tests at the same time against different machines running different browsers and operating systems. Essentially, Selenium-Grid support distributed test execution. It allows for running your tests in a distributed test execution environment.

Note: Selenium Gride is totally different then Webdriver/RC/IDE. 

Please refer: http://www.seleniumhq.org/docs/07_selenium_grid.jsp for more details