Confused on all the games in the Guild Wars franchise, help?

I am about to buy Guild Wars, and I am a bit confused by all the games for sale.

There is Guild Wars GotY for $20, Eye of the North for $20, Factions for $30, and Nightfall for $30. Then there is the trilogy that includes Guild Wars, Factions, and Nightfall for $30. So I could buy each game excluding Eye of the North for $30 or each one separately for $80? It seems slightly odd.



Also, from what I can tell Eye of the North is the only expansion for Guild Wars, then how does Factions and Nightfall fall into the game? Are they completely different games with completely different worlds/characters/etc? Just a bit confused by all this and would love an easy explanation.Confused on all the games in the Guild Wars franchise, help?
Each game is a different storyline with different characters and different abilities. At the same time once you finish them, you can bring your character to the other factions and storylines and just play through them again. It's best to get all of the games in order to get all of the character types, plus all of the abilities available for unlocking. Without all of them, you will see yourself at a disadvantage for not having certain skills or powers int he game.