What is the difference between Selenium IDE, selenium Webdriver and selenium Grid?

SeleniumIDE is a firefox extension used to automate web application on firefox only so we can't perform compatibility testing using SeleniumIDE.(javascript based only)

Selenuim webDriver performs operation on multiple browser with TestNG and Exception handling and it can execute exe file as well as java script also. (written in java and we can run javascript and vbScript)

Selenium Grid is used to execute test cases on multiple machines(compatibility testing) via single remote machine code is written in xml file and java code communicate with xml.

Selenium grid lets you distribute yourtests on multiple machinesand all of them at the same time. this greately helps in reducing the time of tests ,hence you can execute test onwindows and safari on MAC machine using same test script

Selenium grid lets you distribute your tests on multiple machines and all of them at the same time. Hence you can execute test on IE on Windows and Safari on Mac machine using the same test script (well, almost always). This greatly helps in reducing the time of test execution and provides quick feedback to stack holders.

Since I am not I.T, honestly I have no idea

Selenium IDE

1. Only works on Mozilla Firefox

2. Record and play/run tool

3. No server required to start

4. Core engine is JavaScript based

5. Very simple to use. If using User extensions, you require knowledge on java script which makes the work a little bit tough

6. Cannot move mouse with it

7. Full xpaths have to be appended with 'xapth=\\\\\\\\' syntax

8. No Listeners

9. Cannot test iPhone/Android applications

Selenium grid

Selenium grid lets you distribute your tests on multiple machines and all of them at the same time. Hence you can execute test on IE on Windows and Safari on Mac machine using the same test script (well, almost always). This greatly helps in reducing the time of test execution and provides quick feedback to stack holders.

Selenium IDE is the simplest tool in the Selenium Suite and is used as a proto typing tool.

Selenium Webdriver is designed to give more concise programming interface.

Selenium Grid specializes on running multiple tools.

Selenium IDE -is a complete integrated development environment ide for selenium test.

Selenium grid lets you distribute your tests on multiple machines and all of them at the same time.

SELENIUM IDE:to complete integrated development for selenium test .

SELENIUM GIRD:T0 run test different machine .

Selenium IDE -is a complete integrated development environment ide for selenium test. Selenium Grid- allows you run test on different machines.

The selenium IDE (is a plugin to firefox) to record and playback tests (like WinRunner, QTP). You can then export the recorded test in most language e.g. html, Java , .net , perl , ruby etc. The exported test can be run in any browser and any platform using selenium remote control. The Selenium webdriver is a web application testing framework that allows you to write tests in many programming languages like Java, C#, Groovy, Perl, PHP, Python and Ruby, while the Selenium Grid is a smart proxy server that allows Selenium tests to route commands to remote web browser instances. Its aim is to provide an easy way to run tests in parallel on multiple machines.

Selenium IDE is  a GUI Plugin Used for rapid Prototyping of test cases in HTML .

Selenium WebDriver is the actual core API which has bindings in a range of language and allows you to write standalone test 

Selenium Grid is a Execution of the test scripts only not creation