1. Key Difference 1: Project and Dependency Management - Apache Maven is a build automation tool that focuses on project object model (POM) based project management. It uses a XML-based configuration file to define project dependencies, build process, and project structure. TestNG, on the other hand, is a testing framework that does not handle project management. It is mainly used for implementing and executing test cases.
2. Key Difference 2: Test Execution - Maven is primarily used for building projects and executing the build lifecycle phases defined in the POM. It can be configured to execute tests as a part of the build process, but the main focus is not on test execution. On the contrary, TestNG is specifically designed for testing and provides various features like parallel test execution, test dependency management, and comprehensive test reporting.
3. Key Difference 3: Test Annotations - TestNG offers a rich set of annotations that can be used to define test methods and control the test execution flow. These annotations include @Test, @BeforeTest, @AfterTest, @DataProvider, etc. Maven, being a build automation tool, does not provide any specific test annotations. It mainly relies on the test framework being used (like TestNG or JUnit) to define test annotations.
4. Key Difference 4: Reporting - TestNG provides detailed and customizable test reports with features like test case status, time taken for each test, configuration parameters, and more. Maven also generates test reports, but the level of customization and detailed information provided by TestNG is more extensive.
5. Key Difference 5: Integration with Continuous Integration (CI) - Apache Maven is widely used in CI environments like Jenkins, where it can be integrated to automate the build and deployment process. It provides plugins to interact with CI tools and execute tasks like triggering test execution, reporting, and artifact generation. TestNG can also be used in CI environments, but it is more commonly utilized for test execution and reporting within a build process managed by Maven.
6. Key Difference 6: Test Configuration - TestNG allows the use of XML configuration files for defining test suites, test parameters, and other test-related configurations. It provides flexibility in configuring and running tests in various environments. Maven, however, does not offer specific XML-based test configuration. It relies on the underlying test framework (like TestNG or JUnit) for test configuration.

In Summary, Apache Maven is a build automation tool that focuses on project and dependency management, while TestNG is a testing framework specifically designed for implementing and executing test cases. TestNG provides features like test annotations, comprehensive reporting, integration with CI tools, and flexible test configuration, which are not covered by Maven.