What does it mean to download quest helper for WOW via curse client?

Im rather new at world of warcraft still so don’t yell at me if this is a stupid question lol but i downloaded quest helper a long time ago and I need to update it and I saw that you can download it via curse client but I don’t know what that means :/

World of Warcraft Cataclysm Trailer **BLIZZCON 09 NEW** **Official Trailer**

The Official Trailer for the new Expansion Pack for WoW