Disney dollars are gift certificates that can be used to pay for just about everything in the parks, disney stores, disney hotels, restaurants-you get the picture. They come in $1,$5, and $10 denominations with different disney characters on each.
Many people like to redeem awards for Disney dollars since they are only good at disney and it takes the temptation away to spend that money somewhere else. Kids love them and many people give them as gifts for their children to spend at the parks.