What is difference between manual and automated testing ?I

Manual testing test engineer execute test cases manual and automation testing test cases executed in using automated tool or writing test scripts .

Manual Testing

I hope this is self-explanatory. No automation tools like Selenium or HPE UFT are utilized to test the AUT. Instead the designed test cases are run manually by the testers, i.e. manually checking different functional / non-functional flows. It requires business, domain & application knowledge to successfully test an application. The advantage – as it’s not scripted, a tester can follow ad-hoc tests as well while doing test execution (that results in more defects.

Automated Testing

Wouldn’t it be great if computer can run the tests on an application all by itself? 

Software-testing

Automation testing refers to a test method wherein tools like Selenium, UFT, JMeter, LoadRunner, etc. are utilized to script (or record-&-play) the test cases which can then be run by the computer at any time. The advantage – why waste manual efforts on tests which are frequently repeated (i.e. regression tests). Additionally automated tests can be executed on different machines with different OS platform combinations, concurrently. The catch – requires programming skills ;-)

Note: Most projects will have a hybrid approach utilizing Manual tests for functional testing & automation for regression testing. In fact, both testing techniques are 100% necessary and complement each other in multiple ways. Though automation testing cannot ever replace manual testing, but the focus is now shifting towards professionals with both manual + automation experience.