In Norway we use the currency "kroner", but debit or credit cards are accepted more or less everywhere.
The "kroner" is subdivided into 100 "øre", similarly to American pennies or British pence. "Øre" is no longer in circulation and have existed only electronically since 2012.
Debit or credit cards are accepted almost everywhere and is the normal method of paying in Norway. Bills and coins are less and less used here, but it is still a good idea to have some cash on you. Note that foreign currency is rarely accepted. Most places that receives a lot of tourists will accept more or less all large credit cards.
Cash machines and ATM's can be found everywhere in larger towns and cities. They are normally marked with the sign "Minibank", "ATM" or "Cash Machine". In more rural areas you will also be able to find cash machines at for instance petrol stations.
The most commonly accepted credit cards are Visa and MasterCard, while Amex and Diners are not accepted everywhere. It's always a good idea to check before shopping if you are in doubt.