The first principle, articulated by Rawls, is known as the liberty principle. This states that all individuals must be guaranteed a set of basic rights (e.g., respect for one's life, moral integrity, and essential freedom).
The second principle is known as the difference principle and stipulates that economic prosperity should be re-invested into the least-advantaged segment of the population (e.g., those lacking in basic provisions, necessities, and needs), rather than in other projects (e.g., concentrations of state power or imperialist ambitions). Note that none of this implies theft from the most prosperous or complete economic equality. In fact, most inequalities would be legitimate under this system, provided that those inequalities serve the least advantaged members of society.