Iranian Rial and Toman are the currencies of Iran but toman is no longer an official currency. One toman equals 10 rials and Iranians normally express prices of goods in toman.
For exchanging money, you can refer to the banks or authorized exchange shops (“Sarrafi” in Farsi) at the airports or tourist areas. There are also street exchangers in tourist areas who offer marginally better rates than the banks.
USD, EUR, GBP, AED are wildly-accepted currencies and can be exchanged almost everywhere, but other currencies can be exchanged in certain banks.
Iran is still a cash economy so foreign credit cards and travelers cheques are not a reliable way for bringing money to Iran, as those are not accepted anywhere.
After all, it is recommendable to bring money only in cash in USD, EUR or GBP. To keep your money safe, using a money-belt is proposed.