Technically speaking, mods can be uploaded just about anywhere since mods are just a bunch of files with customized code. This means that mods can be anything from replacing dragons with Thomsas the Tank Engine to creating entire DLCs with its own quests, NPCs and features. These mods can vary in size and quality, and the game objects they modify can differ.
So Skyrim mods refer to modifications specifically geared toward modifying the game in some capacity. They refer to tweaks, additions, changes, subtractions or anything that modifies a game or program-hence the name. At its most basic level, “mods” refer to modifications that can be made to games and programs.
