NSP files are typically used for homebrew-enabled or modified consoles (running SX OS or Atmosphere) to install updates from unofficial sources. How to Use (Context: Modified Switch)
Sometimes updates are required to use new DLC content. POKLGEV-(RF)-UPDATE-NSWTCH-NSP-ZIPERTO.rar
A Nintendo Submission Package. This is the digital format of a switch game, similar to a digital cartridge or eShop file. NSP files are typically used for homebrew-enabled or
Means this update will work on a Switch console regardless of its region (e.g., US, Europe, Japan). POKLGEV-(RF)-UPDATE-NSWTCH-NSP-ZIPERTO.rar
This is a software patch for the game. It does not contain the base game itself, only the files needed to upgrade a lower version to a higher one. NSWTCH: Indicates it is for the Nintendo Switch console.