Discretionary spending is the part of the federal budget that goes through the appropriations process, which lawmakers have an option to change. This is comprised of non-defense discretionary funding and defense discretionary funding.
Congress allocates discretionary spending on an annual basis. As of 2014, discretionary spending for defense makes up the majority of all discretionary spending. Other discretionary spending includes education, federal agencies, research grants, foreign investments and the national park system.
The other type of budgetary spending is mandatory spending, which does not have an annual limit or appropriations process. This type of spending includes Medicare and Social Security as well as interest on the debt.