Social justice refers to how the benefits and hardships are distributed to individuals or groups in a society (Miller, 1999). Social justice is traditionally tied to the concept of distributive justice, and can be used interchangeably. It thus refers to the equitable and/or fair distribution of social resources or public goods among members of society. What it means in practice is debated among most contemporary philosophers as what is 'fair' or 'equal' and what constitutes 'social resources' or 'public goods' are not clearly delineated and somewhat ambiguous.
Source: Miller, D. (1999). Principles of social justice. Harvard University Press.