The federal deficits are how much money the country lost when you count the revenue it made from taxes and the expenditures it had to cover. When a budget gets less revenue than it spends, then a deficit is made. Having a deficit in the budget does not mean that you're indebted, nor does having a surplus mean that your debt is non-existent.
The federal debt is the amount of money that the government of the United States is indebted after a deficit happens in the budget. The debt is the combined amount of all deficits from year to year and having a surplus helps repay the debt. For example, the Clinton presidency had a surplus in the budget for a few years, but the surplus was not as large enough to erase the overall debt of the federal government.
There are numerous parts of the federal expenditures which are uncontrollable because you cannot know how much money is actually going to go on that. For example, it's relatively easy to build a defense budget since you know precisely what you're paying and how much, however, the uncontrollable part comes from various funds that are not used by everyone and not everyone reaps the benefits. For example, national disasters are common in the US such as hurricanes or tornadoes or similar things and you can never know how much money as a government you're gonna have to spend on mending problems made by those disasters. Another thing is various welfare programs where the number of applicants changes sometimes drastically.<span />
