Georgian currency is Lari and is denoted by GEL. 1 Lari is divided into 100 Tetri, i.e. cents.
Official exchange rate of Lari against foreign currencies:
When exchanging money in banks be sure to present your ID. With the small exchange cabins available almost anywhere in the country this is not necessary. These cabins may also have slightly better exchange rates.
When traveling out of Tbilisi and in need of Georgian Lari, be sure to exchange money before the trip as exchange rates are worse in rural areas. Georgian Lari is a closed currency, so be sure to change the remainder of your money back before leaving the country.
Most importantly, be aware that some ATMs in Georgia may not accept foreign cards (though this is not usually a problem in Tbilisi). This can be a potentially serious problem if you are caught without cash during non-business hours or on weekends, so have some cash. Also, while prices are generally very reasonable in Georgia, a side effect is that many small establishments and taxis will not have change for large Lari notes (especially 50 or higher), so travelers are advised to carry plenty of smaller notes and coins.