"Congress annually considers several appropriations measures, which provide funding for numerous activities, for example, national defense, education, and homeland security, as well as general government operations. Congress has developed certain rules and practices for the consideration of appropriations measures, referred to as the congressional appropriations process. Appropriations measures are under the jurisdiction of the House and Senate Appropriations Committees. In recent years these measures have provided approximately 35% to 39% of total federal spending. The remainder of federal spending comprises direct (or mandatory) spending controlled by House and Senate legislative committees and net interest on the public debt. […] Each year Congress considers a budget resolution that, in part, sets spending ceilings for the upcoming fiscal year. Both the House and Senate have established parliamentary rules that enforce certain spending ceilings associated with the budget resolution during consideration of appropriations measures in the House and Senate, respectively. Congress has also established an authorization-appropriation process that provides for two separate types of measures--authorization bills and appropriation bills. These measures perform different functions. Authorization bills establish, continue, or modify agencies or programs. Appropriations measures subsequently provide funding for the agencies and programs authorized."
CRS Report for Congress, 97-684