An ETL Tester validates data extraction, transformation, and loading processes within data warehousing. Their significance lies in ensuring data integrity and accuracy for informed decision-making. Key responsibilities include designing test cases, executing tests, and documenting results. Required skills encompass SQL proficiency, data modeling, and analytical thinking. Typically working in IT teams, ETL Testers collaborate with developers and data analysts. Career progression may lead to roles like Data Analyst or QA Manager, enhancing growth opportunities in the data domain.