In the Constitution, what does the phrase promote the general Welfare refer to?

In the Constitution, what does the phrase "promote the general Welfare" refer to? People are naturally self-centered, and a government is necessary to keep order.
Slavery is immoral, and a government is required to end slavery.
People are naturally greedy, and a government is required to form charitable organizations.
Businesses are immoral, and a government is required to resolve disagreements over prices.