The file format (Nintendo Submission Package), which is the standard format for digital eShop games.
Files from sites like Ziperto are frequently used to play games on modified (jailbroken) consoles or emulators like Yuzu or Ryujinx. If you are downloading these, be cautious of pop-up ads and ensure you have a reliable antivirus, as "repack" sites can sometimes host malicious links. IB-(USA)-NSwTcH-[BASE]-NSP-Ziperto.rar
This indicates it is the core game file, not an update (UPD) or downloadable content (DLC). The file format (Nintendo Submission Package), which is