Each character begins play with a number of gold pieces that he can spend on weapons, armor, and other equipment.
As a character adventures, he accumulates more wealth that can be spent on better gear and magic items. Table: Starting Character Wealth lists the starting gold piece values by class. In addition, each character begins play with an outfit worth 10 gp or less. For characters above 1st level, see Table: Character Wealth by Level.
The most common coin is the gold piece (gp). A gold piece is worth 10 silver pieces (sp). Each silver piece is worth 10 copper pieces (cp). In addition to copper, silver, and gold coins, there are also platinum pieces (pp), which are each worth 10 gp.
The standard coin weighs about a third of an ounce (50 to the pound).
Merchants commonly exchange trade goods without using currency. As a means of comparison, some trade goods are detailed on Table: Trade Goods.
In general, a character can sell something for half its listed price, including weapons, armor, gear, and magic items. This also includes character-created items.
Trade goods are the exception to the half-price rule. A trade good, in this sense, is a valuable good that can be easily exchanged almost as if it were cash itself.