QA testers, or Quality Assurance testers, are professionals responsible for ensuring that software applications function correctly and meet specified requirements. They identify bugs and issues by running various tests, documenting their findings, and collaborating with developers to resolve problems before the software is released to users. Their work involves creating test plans, executing test cases, and using automated testing tools to streamline the process. By thoroughly evaluating software, QA testers help improve user experience and maintain the quality of products, ultimately contributing to the success of the software development lifecycle.