Patch - Wowpedia - Your wiki guide to the World of Warcraft
A patch or build is an update to the game files. Expansions (Patch X) are the most massive type of content patches, adding entire new continents, new playable races or classes, multiple zones, dozens of instances and other game features. Major patches (Patch X.Y) can include new instances, zones and features. Minor patches (Patch X.Y.Z) can also add new game features, instances and scenarios, but tend to focus on updates such as balance changes. Hotfixes are small, instant changes to the game, which are done server-side and require no download or server takedown.[1]
https://wow.gamepedia.com/Patch
