: Short for Decrypted , meaning the game data has been processed so it can be played directly on PC emulators like Citra without needing a console's unique encryption keys.
The filename refers to a compressed archive containing a decrypted ROM for the Nintendo 3DS game Senran Kagura 2: Deep Crimson . Breakdown of the Filename SK2DC-USA-DecrTD-Ziperto.rar
Which you're planning to use (Citra, Lime3DS, etc.)? If you need help extracting the contents? : Short for Decrypted , meaning the game