What does provide for the public welfare mean?

The preamble to the Constitution of the United States of America lists several reasons for why the people came together to ordain and establish that constitution. Of the reasons listed, to provide for the general Welfare of the people has been one of the responsibilities tasked to that government and of all the demands made of that government this particular one is perhaps the most contentious. What does it actually mean to provide for the public welfare? Conservatives believe The United States government has expanded beyond its constitutional boundaries with a liberal reading of this phrase. Many believe that in order to provide for the general welfare the government must provide for the needs of those individuals not capable of providing for themselves. But the extent of this directive is a cause for great political debate when weighing the directive against its costs.