Discretionary spending is a spending category through which governments can spend

Government spending

Government spending includes all government consumption, investment but excludes transfer payments made by a state. Government acquisition of goods and services for current use to directly satisfy individual or collective needs of the members of the community is classed as government final...

 through an appropriations act. This spending is optional as part of fiscal policy

Fiscal policy

In economics and political science, fiscal policy is the use of government expenditure and revenue collection to influence the economy....

, in contrast to entitlement programs for which funding is mandatory.

In the United States, discretionary spending refers to spending set on a yearly basis by decision of Congress. Such spending is usually authorized by Congress in another act. Provisions of an appropriations act that authorize spending are earmarks

Earmark (politics)

In United States politics, an earmark is a legislative provision that directs approved funds to be spent on specific projects, or that directs specific exemptions from taxes or mandated fees...

. When an authorization act also appropriates funds, it is called mandatory spending

Mandatory spending

In economics, mandatory spending is spending on certain programs that is required by existing law.In the United States, mandatory spending refers to budget authority and ensuing outlays provided in laws other than appropriations acts, including annually appropriated entitlements...

.