Gems - A currency that bridges the exchange of currencies between Titan.TF and the Team Fortress 2 game. Gems can be used to buy Team Fortress 2 items, and vice-versa can be purchased with Team Fortress 2 items at a rate of 900 gems / scrap. They can be converted into Titan Credits at a rate of $0.30 / gem. However, please note that Titan Credits cannot be converted back into Gems. They can also be used to purchase some other items such as EXP Packs (to increase your XP instantly).
Titan Account - An account that exists on the Titan data servers, which contains all of your existing Titan.TF data. This includes credits, gems, experience points, inventory items, etc.
Titan Credits - Also known as money. This is the main currency used to purchase items from the item shop. The symbol is denoted as $.