Justice is a very extensive concept that concerns many sectors : philosophy, moral, religion, law... It refers to the moral principle of conformity to positive law and natural rights.
A person who is fair is a person who has a moral judgment and a willingness to equity.
Justice is hard to define, even today the experts don't agree on its definition.
“What is justice?” is a question that has been tormenting philosophers since antiquity.
Moral justice, different from institutional justice, refers to the act of favoring respect and equity for all. This type of justice is considered innate for every individual. We all have a “sense of justice” that gives us the ability to see what’s fair or not. Even children have their own idea of what’s fair or not.
However, the personnel practice of justice can be very different from what most individuals and institutions consider as morally fair. For example, one can wish to take justice into their own hands which would imply going against moral rules by hurting or killing someone (see vengeance).
The notion of justice is relative: what seems fair for one can seem unfair for others.
One may doubt the existence of absolute justice because in a conflict of interest, there will always be someone who’ll be penalized. Furthermore, this notion changes according to different cultures and societies : the law and the system changes from one country to another.