Patches are a critical component of any PC game. They allow the developers to support the game post-release with enhancements such as (but not limited to):
For the modern gamer, getting a game patched to the latest release is trivial. Game distribution clients like Steam and Origin have auto-patching built-in, automatically retrieving the latest patch from the store's servers. Even standalone games that do not rely on a store client have some form of auto-patching included.
However, older games with a retail release (i.e. any game before 2009/2010) normally do not have this functionality included or the functionality is not entirely reliable. Instead, it is up to the user to download the official patch files either from the developers themselves, or a 3rd party site that hosts these files.
For the wiki, the Patches subsection will handle all patch listings for the retail version of the game.