ING Direct is a savings account, so your money is guaranteed by the government (FDIC).
They have multiple types of accounts, you just have to choose one that's best for you.
CDs are contracts where you lend the bank a certain amount of money for a set amount of time. They then pay you interest. The worst thing about CDs is that it's hard to withdraw money except at designated times, which is inconvenient. A savings account like ING can get you pretty good rates comparable to CDs.
With $800, you should probably just put it in a savings account and not do anything too fancy with it. Having a savings account puts you a step ahead of other 20 year old already.