Currencies are items which can be exchanged and are commonly used for various transactions in RuneScape.
Coins (or gold pieces - "gp") are the main form of currency and are almost universal, as they are accepted by most NPC's and are the currency used by the Grand Exchange. All other currencies may only be used at their specific location. Only trading sticks are comparable to gold pieces in that they can be used to buy and sell items in multiple places as well as to trade with other players, although their usage is much more limited than usage of gold pieces. Minigames often have dedicated currencies associated with them.
Occasionally, Spirit shards are used by players as a currency to buy highly expensive, rare discontinued items such as partyhats, to circumvent the max stack limit.
Many currencies are virtual (or kept 'on record') and don't exist in an item form. Thus, these do not take up inventory or bank space, and only appear in specific interfaces. This also makes them untradeable. For example, Pizazz points are stored in a Pizazz hat, and thaler are displayed only in Stanley Limelight Traders store.