A money market account is a savings option that can give you a little more for your money than a traditional savings account.
How does this work? Money market accounts typically have restrictions on how frequently you can access your money, and may also require you to maintain a certain minimum balance to avoid fees. Knowing that customers' deposits in these accounts are going to fairly stable gives the banks more latitude to invest those funds in short-term, fixed-income financial instruments (otherwise known as "money market instruments").
This additional investment flexibility pays off in the form of higher interest rates, which the bank can pass along to you as a depositor.