Automation testing is an Automatic technique where the tester writes scripts by own and uses suitable software to test the software. It is basically an automation process of a manual process. Like regression testing, Automation testing also used to test the application from load, performance and stress point of view.
In other words, Automation testing uses automation tools to write and execute test cases, no manual involvement is required while executing an automated test suite.
The main goal of Automation testing is to increase test efficiency and develop software value.