See Resources (for Resource buildings)
There are four types of Currency in the game; Resources (Metal, He3 and Gold); Mall Points (the Premium currency); Tokens (Badges/Honor/Champion points, collected to buy special items) and Vouchers (a limited currecncy).
Like most Freemium games, the Premium currency 'Mall Points' can be used to aid you in pretty much everything from Research, ship production and speed up upgrades and so forth, there are also Vouchers which can be used to speed up Research and Building Upgrades and purchase a few (very limited) items from the Web Mall (the games shop), these are free and are given (in a small amount) as a daily collectable.
The 3 resources in Galaxy Online II are:
Gold - Produced by Residential areas, produces the most income and is used for Research, trade, and is also required for upgrading buildings. (~2x more produced than metal or he3) All resources are stored in the Resource Warehouse, which has limited capacity requiring the player to collect from it every 12 hours or less, see also trading center for more about gold.
All 3 of these resources can also be obtained from attacks on other players.
The remaining in game currencies in detail are:
Mall points - The game's Premium currency. Can be used to purchase a wide variety of items from both in-game shops and other players. In order to sell an item to another player for mall points, a minimum amount is required to be purchased from IGG due to the auction placement fee.
Vouchers - These are similar to mall points, but you cannot buy many mall items with them, they also cannot be donated to the corp. Vouchers are difficult to get in large quantities, but are useful in and are free. They can not speed up ship production but can speed up ship repair, they can be used to speed up building construction/upgrades and they can also be used to purchase extra spins on the Lucky Wheel as well as a few special items in the Web Mall, like Advanced Truce cards.
Badges - Used to purchase special items in Badge category on the Web Mall, Earned by completing Restricted Instance, also when completing various tasks in the game, for instance you can earn 1 additional badge for selecting "post this to facebook" after completing a restricted instance. You can also earn up to 100 badges from I.G.L.
Honor Points - Used to purchese special items in the Honor category on the Web Mall, These are earned by competing in the League Matches against other players, the amount awarded varies by your League level, you may also earn many Honor points (15 to 255) if your corp clears a Pirate Challenge. You can also earn up to 100 honor points from I.G.L.
Champion Points - Used to purchase specialty items on the Champion's Mall, a new feature added on 4Jul13. At this time, one can only gain Champion Points via participation in Championship matches occurring once per week. You can also earn up to 150 Champion Points per day from the I.G.L.