Rawls on Social Justice
Rawls sets his theory of justice against the utilitarian tradition of justice. When Rawls uses the word "justice", he means social justice. He argues that the traditional theory of utilitarianism proposed by John Stuart Mill and Jeremy Bentham "the greatest good for the greatest number of people" is the theory that is closest to our intuitive notion of justice. However, Rawls critiques this traditional form of utilitarianism in the following quote: "[utilitarianism] adopt[s] for society as a whole the principle of choice for one man.” By doing this, Rawls argues that "[utilitarianism] fails to take seriously the distinction between persons."
The Original Position
The Original Position is Rawls' version of social contract theory. It is purely hypothetical, thus Rawls argues it has a higher level of abstraction than the conceptions of "states of nature" offered by Hobbes, Locke, Kant, and Rousseau. Because societal institutions color and bias our view of the institutions, Rawls sets up a thought experiment to create distance from the institutions. Essentially, what principles of social justices would be chosen by parties who have knowledge of human interaction, but are deprived of the knowledge of their position in society. The lack of knowledge of your position in society is what Rawls calls the "Veil of Ignorance".
For example, it is undeniable that a cisgender heterosexual white male born into a middle class family has more social goods and privilege than a bisexual Asian trans woman born into a middle class family. The purpose of the original position is to strip away the preconceived privileges to rationally create a society where social goods are distributed fairly that will benefit the least advantaged in society.
The Veil of Ignorance
The Veil is essential to Rawls' thought experiment. It assures that those inside the Original Position are choosing the formulation of social justice that benefits everyone in society without concerning their natural ability, talents, their social background, or their society's historical circumstances. The information that Rawls does offer from inside the Original Position and behind the Veil of Ignorance are: (A) material goods are scarce, but only moderately so, and (B) there are a plurality of conceptions of the good based on different world views.
The objection offered is if you are completely ignorant of all aspects of society, how do you choose how to structure the society for social justice? Rawls heads off this object by offering a set of "primary goods". These primary goods are: rights, liberties, social bases of self respect, and opportunity in both income and wealth. Rawls postulates that the parties in the original position will prefer more primary goods than less primary goods. 
In the drive for acquisition of primary goods, the parties inside the OP and behind the Veil are described as "mutually disinterested." What Rawls means is each party is motivated to obtain as many primary goods as they can, but does not care if others obtain primary goods.  This not Rawls attempting to ascribe something to human nature, it is a reaction against the prevailing sympathetic-spectator theory inside ethics popularized by David Hume. Rawls objects to this in two ways. The first is it neglects the individuality of persons (in a similar way that utilitarianism neglects this when adding up total happiness)  or if they attempt to avoid the use of utilitarian aggregation, they will not be able to answer the questions of human conflict, if the sympathetic viewer is completely sympathetic and benevolent to all persons. Rawls argues that the combination of mutual disinterest and the Veil of Ignorance surpasses these issues by achieving a similar moral equivalence to universal benevolence without neglecting the individuality of persons or sacrificing the results to perpetual questioning. 
American political philosopher Michael Sandel offers an objection to Rawls' use of the veil of ignorance, arguing that even as a hypothetical it does not work because of certain innate qualities. Sandel argues that family ties are not consciously acquired, for example, and it is therefore impossible to separate yourself from such ties. Rawls in opposition to this objection argues that his Veil of Ignorance is not a metaphysical theory, but a political theory, which allows and overriding consensus could be formed by political groups based on different moral or political views.
Justice as Fairness
This concept of justice that Rawls proposes which benefits the least advantaged in the social lottery so they are not hurt or forgotten.
The Liberty Principle as presented in A Theory of Justice is the most extensive basic liberty compatible with a similar liberty for other members of society. Rawls later amended this in Political Liberalism to the following: "each person has an equal claim to a fully adequate scheme of equal basic rights and liberties" 
Rawls uses the Equality Principle to ground what he calls distributive justice. This is his theory of how to allocate social goods inside society.
Fair Equality of Opportunity
Rawls argues that equality of opportunity to offices and positions should be open to any member of society regardless of their starting social position. Rawls distances himself from formal equality of opportunity by arguing that not only should all members have the right to strive for positions and offices, but that they should have effective equality in obtaining offices and positions as compared to another with similar natural abilities. 
The purpose of the Difference Principle is to regulate inequality in society. Rawls compensates for naturally occurring inequality by ensuring that the worst off in society receive a fair deal. An inequality is allowed as long as it works to the advantage of the worst off in society.
Advantages to Rawls' Theory of Justice
Rawls' conception of justice allows a liberal democratic society to effectively account for plurality in a society while still benefiting those who are disadvantaged from birth. It also does not suffer from the problems that are entailed with equality of outcome by being a theory that promotes equality of opportunity.
By assuming the lack of benevolence governing society, the scarcity of resources, and mutual disinterest, Rawls' version of the social contract is particularly valuable in state building. It is designed to setup the most flexible liberal state that endorses plurality and is prepared for the worst case scenario of governance.
Disadvantages of Rawls' Theory of Justice
Rawls' theory was criticized by feminist philosopher Susan Okin. While Rawls dealt with societal injustice, Okin argues that Rawls account of justice fails to address injustice and hierarchies inherent to familial relations. Okin also criticizes Rawls for not accounting for gendered division of labor and patriarchal social institutions.
Charles W Mills has offered criticisms of Rawlsian framework as not being able to address racial injustices and focuses too much on ideal theory . Tommie Shelby has responded to Mills . Mills has responded to this criticism . The positions that these two philosophers take are not radically different. Both believe that Rawlsian approaches are still useful in approaching racial justice, but Mills wishes to radically restructure Rawls where as Shelby does not wish to restructure Rawls as radically. Mills main concern with Rawls is that his system does not have principles for rectification of historical racial injustices and this is accurate. However, Rawls does not offer any principles for rectification of any historical injustice. It is also important to note that Mills (as Shelby does point out) does not offer any substantive positive alternatives to the Rawlsian school of thought, merely criticisms, which are not completely unfounded.
Mills does raise valid and serious concerns that liberalism was founded by racists such as Kant, Hume, Locke, and Hegel and people of color are not proportionately represented in modern academic philosophy .
- See the Wikipedia article on John Rawls.
- Ten minute summary of Rawl's Theory of Justice
- Internet Encyclopedia of Philosophy on Rawls
- John Rawls, influential political philosopher, dead at 81, by Ken Gewertz
- A Theory of Justice Rawls, ISBN:0-674-00078-1
- Rawls 1999, pg. 123
- Rawls 1999, pg. 12
- Rawls 1999, pg 164
- Rawls 1999, pg 128
- John Rawls, Political Liberalism 2005 ISBN: 0231130899 pg. 5
- Okin, Justice, Gender, and the Family (New York: Basic Books, 1989)
- Rawls on Race Mills, W C. 2009 http://havenscenter.wisc.edu/files/Mills-Rawls%20on%20Race.pdf
- Racial Realities and Corrective Justice, a response to Charles W Mills Shelby T 2013 http://havenscenter.wisc.edu/files/Mills-Rawls%20on%20Race.pdf
- Retrieving Rawls for Racial Justice? A Critique of Tommie Shelby Mills, W C. 2013 http://muse.jhu.edu/login?auth=0&type=summary&url=/journals/critical_philosophy_of_race/v001/1.1.mills.pdf