This is a compressed archive file. To use it, you would typically need to extract it using a program like WinRAR or 7-Zip to reveal the .3ds or .cia game file inside. What’s Inside? If you were to play this, you’d find:
Since this is a fan-made mod distributed via third-party sites, always ensure your antivirus is active when handling .rar files from the internet, as these communities are unofficial. GlowingGarnetRemixv2Citra-pokemonerdotcom.rar
This indicates it is the second version of the "Remix" update, which usually includes updated textures, custom "Delta" species (Pokémon with different types than usual), and increased difficulty. This is a compressed archive file
Often, these hacks allow you to catch all 721 Pokémon available up to Gen 6 without needing to trade. which usually includes updated textures