A manual testing developer engages in the process of manually checking software for defects, ensuring that applications function correctly. They design and execute test cases, report bugs, and verify fixes. On the other hand, an automated testing developer uses software tools to run detailed, repetitive, and data-intensive tests automatically. They write scripts, automate test cases, and analyze the results. Both roles aim to deliver a reliable, high-quality software product by identifying and fixing issues early in the development cycle. They contribute significantly to enhancing the user experience and meeting business requirements.