The government can be viewed as a money pump that continuously circulates its own currency. The outflow of spending is matched by the inflow of revenues from taxes and bond sales. This flow engages the private sector in useful work that would not otherwise be performed under private initiative. An example is the building of the interstate highway system. The outflow includes various subsidies and transfer payments that do not directly support work, but are important in maintaining purchasing power.
All flows involve some redistribution of income.
They are beneficial to the extent that they efficiently contribute to a decent standard of living for the entire domestic population. Essential spending includes what is required to maintain a modern infrastructure, establish law and order, and provide for national defense. Further spending becomes detrimental when it engages resources, including manpower, currently in demand by the private sector. But if the private sector is operating below its productive capacity for lack of sufficient purchasing power, additional government spending will be beneficial. Deficit spending adds to the aggregate demand of the private sector.