A. For purposes of determining inadmissibility, “public charge” means an individual who is likely to become primarily dependent on the government for subsistence, as demonstrated by either the receipt of public cash assistance for income maintenance or institutionalization for long-term care at government expense.

A number of factors must be considered when making a determination that a person is likely to become a public charge.

Under Section 212(a)(4) of the Immigration and Nationality Act (INA), an individual seeking admission to the United States or seeking to adjust status to that of an individual lawfully admitted for permanent residence (Green Card) is inadmissible if the individual, “at the time of application for admission or adjustment of status, is likely at any time to become a public charge.” Public charge does not apply in naturalization proceedings. If an individual is inadmissible, admission to the United States or adjustment of status is not granted.  Much more here from USCIS.