The game has two sides, some players focus on one and some play both, these are PvE and PvP. The PvE environment consists of following the story through the game, fighting mobs and once you have completed the game you have the challenge of hard mode, where even in the starter areas, mobs are high level and require a well planned human group to execute. There are also rewards in the form of valuble loot and titles which your character can display, such as for completing all the missions, exploring the map, capping elite skills or killing all of the foes in hard mode.
PvP or player vs player consists of Guild vs Guild matches with teams of 8 players, 4v4 team arenas or 8v8 heroes ascent, where a victory claims the hall of heroes for the continent on whose server you play. With the purchase of Guildwars: factions, alliance battles are also unlocked which give 12v12 fights for your chosen faction. Again, titles are available to show your skill for many aspects of these.
On a more practical note, comments which note the downloading time are valid, however this is reduced by installing from a game CD rather than online, in general once the initial update, the more regular updates take less than 5 minutes to complete.
Overall, definitely worth purchasing and I haven't grown tired of it after 2 years, the graphics are excellent and they've also recently updated past cutscenes with lip syncing which was a feature previously lacking. The community is great providing you take care selecting a guild (older players might want a guild with a lower age limit if they wish to play with others of their own age) and I've spent MANY hours enjoying this game.

Source:
http://www.amazon.co.uk/NCsoft-Guild-Wars-...5589&sr=8-1To be honest I don't care.