Debt, simply, is money spent today that will have to be repaid at a later time. "The temptation to buy votes from boomers and seniors by piling massive unfunded liabilities on future generations ($74 trillion at last count) seems hard to resist. According to humorist Dave Barry, "it's like going to a fancy restaurant and ordering everything on the menu, secure in the knowledge that when the bill comes, you'll be dead.'" (27).
"[B]oth political parties have formed an unholy alliance an undeclared war on the future. An undeclared war, that is, on our children. From neither party do we hear anything about sacrificing today for a better tomorrow." (28). In a very real way then, decisions today to spend more money than is brought in are expenses which young Americans and future generations will be left to figure out how to pay off.
See Senator John McCain answering a question from the Association of Young Americans: