FSA: A flexible spending account (FSA) is a workplace account you can use to pay for certain medical costs that come out of your own pocket, such as insurance copays, prescriptions, and other health-related items and services. The contributions to an FSA are tax-deductible.
HSA: A health savings account (HSA) is an account you can use to pay for a variety of medical costs. Only people with a qualifying high-deductible health plan are eligible. The contributions to an HSA are tax-deductible, and the account's earnings (if invested) are tax-free, as are withdrawals for eligible medical expenses.