Minecraft Java Edition 1.21.2 introduces the "Bundles of Bravery" update, which adds space-saving Bundles, the ability to enable Hardcore Mode in Realms, and baby variants for Dolphins and Squids. It also includes over 300 bug fixes, visual updates like redesigned Redstone Torches, new Banner Patterns, and technical improvements for creators, enhancing the game's performance and features.