For those interested in the technical aspects, Mario Kart 8 Deluxe is available in NSP (Nintendo eShop) and XCI (eXtra Console Installer) formats. NSP is a digital format used by the Nintendo eShop, allowing players to download and install the game directly to their Switch console. XCI, on the other hand, is a file format used by the homebrew community to install and play games on the Switch.
The inclusion of both acronyms in the title——is a strategic move by the uploader. It casts the widest net possible. It signals to the downloader that whatever their specific modded firmware (Atmosphere, SX OS, etc.) requires, this download has them covered. It is a buffet of formats.
The base game. Many players prefer a "SuperXCI" file, which merges the base XCI game, the 3.0.3 update, and all DLC into one convenient file. Content Included in the Definitive Version