Update181 indicates this is update version 1.8.1 for the game.
NSP stands for Nintendo Submission Package , which is the standard file format used for games and updates on the Switch console.
Ziperto is a well-known community site that hosts Switch-related software backups and updates. Usage and Risks Nintendo Switch DLC & Updates - Ziperto
The file is a compressed archive containing a software update for a Nintendo Switch game. Based on the naming conventions used by the source site Ziperto , File Identity Report
