The file has been "decrypted," meaning the Nintendo 3DS encryption has been removed. This allows the game to be played on PC or Android emulators like Citra , rather than requiring a modified ("hacked") physical 3DS console.
Here is an informative breakdown of what this file represents: EOU-TMG-(UNDUB)-DecrTD-Ziperto.rar
This refers to the source website that provides these modified ROMs, which frequently hosts decrypted and undubbed versions of Atlus games. The file has been "decrypted," meaning the Nintendo
These types of files are used to experience the "definitive" version of the game, combining the best aspects of both localization and original audio, playable on alternative platforms. The file has been "decrypted