The currency of Jordan is the Jordanian dinar (JOD), which is divided into 100 piastres. It is a stable currency, and it is pegged to the US dollar.
Money can be exchanged at banks, exchange offices and hotels, and the rates are generally good. ATMs are widely available, and they accept international cards.
It is a good idea to carry some cash, especially for small purchases, tips and the markets. Cards are accepted in hotels and larger restaurants, but cash is king in the souks.
For a visitor, managing money is easy. You can exchange money at the airport, and full package tours include the costs of the main expenses.