The answer is: CD/higher interest rate
CD stands for certificate of deposit. When you open a CD, you agree to store your money in the bank within a specified period of time and the bank would give you a specified interest rate in return.
CD has higher interest rate compared to normal account. But, within that specified period you can take the money that you invested in CD (unless you want to receive penalty) , while you can take your money whenever you like if you open a saving account.