Automation Testing allows executing test cases using automated testing tools to reduce manual testing. It involves recording test cases using tools like Selenium and replaying them repeatedly. This improves return on investment as the same test cases do not need to be run manually for successive development cycles. Selenium is an open source tool that supports testing web applications across browsers. It uses a client library with a JSON wire protocol to communicate with browser drivers to remotely control browsers. Jenkins is a free and open source automation server that facilitates continuous integration and delivery by automating software build, test and deployment processes.