Maven 4 introduces significant improvements after 15 years since Maven 3. Key updates include POM version 4.1.0, build/consumer POM separation for cleaner dependency resolution, new artifact types for explicit classpath and module path control, and renaming 'modules' to 'subprojects' to avoid confusion with Java modules. The release adds a tree-based lifecycle for better multi-project performance, before/after phase hooks, condition-based profile activation, and a unified sources section for custom source directories. An upgrade tool helps migrate from Maven 3, while maintaining backward compatibility with version 4.0.0 POMs.