Currency (GW2)  

Coins

Guild Wars 2 has normal coins in Gold, Silver and Copper denominations.

Gems

Gems are an in-game currency, purchased with real-world money, that can be used to buy helpful items from the Black Lion Trading Company.

Gem value in terms of real world is variable, as the Price per Gem decreases the more you buy at once.

Karma

Through completing non-story quests (like Public Quests) you gain a favorable reputation with the inhabitants of the world. This is recognized as Karma which can be spent with Karma merchants (and many quest NPCs once you complete their task) to buy what most games would think of as quested gear.

Guild Wars 2 Wikibase™ Dictionary