Immigrant Visas
Some foreign nationals are eligible for immigrant status which allows the individual to live and work in the US permanently. To qualify for immigrant status you must fall into one of the following categories: family-sponsored (including immediate relatives of US Citizens), special immigrants, and employer-sponsored immigrants.
To qualify for immigrant status, you must be sponsored into the United States by either an US citizen or permanent resident relative(s), by a prospective US employer, or fit within one of the special immigrant categories. In order to get immigrant status your sponsor must file an Immigrant Petition on your behalf (I-130, I-140, I-360). The sponsor must also submit an affidavit of support (this is a little bit different for employment based sponsorship) attesting that the beneficiary (the sponsored person) will not become a public charge to the government.
Please note that winners of the Diversity Visa Lottery or Asylees with a granted asylum petition do not need a sponsor in order to receive their immigrant visa nor do they need someone to provide an affidavit of support.