This update is considered the final major patch for the game, making the experience more complete than the base 1.0.0 version.
The inclusion of both acronyms in the search string usually means the user is looking for a "Multi-Format" release, or the file can be converted/installed depending on the user's custom firmware (CFW) setup. Metroid Dread SWITCH NSP XCI -Update 2.1.0- -eS...
The terms in your query refer to specific file types used by the Nintendo Switch system: NSP (Nintendo Submission Package) : Typically used for eShop titles and updates. XCI (NX Card Image) : A backup format representing a physical game cartridge. Official updates can be downloaded automatically via the Nintendo Support portal while connected to the internet. Nintendo Support in the new Rush modes? How to Update Metroid Dread | Nintendo Support This update is considered the final major patch