What is the purpose of justice?

Okay Philosophy time:

The main reason Justice is often discussed and is vital to understand is because it is a fundamental social, ethical and moral principle, one that we are forced to confront on a daily basis. Is Justice proactive or reactive? Is it fair? Is it equality? Should people get what the deserve, or what they need?

One way to view Justice is in distribution of commodity, or basically who gets what. In that lens, there is Equality-based-Justice, where everyone gets the same kinds and equal amounts of commodity. Need-based-Justice, where the more someone requires something, the more they should get of it. And finally, Merit-based-Justice, where commodities are distributed based on one's contribution to society, positive or otherwise.

Another way to view Justice is in the statement Justice is fairness. In this way, inequalities should favour the least well-off of society, so as to level the playing field. An example would be the government taking you taxes and spending them on poor people. The argument made here is that people have the rights to basic needs, such as food, shelter, a doctor should they fall ill, etc. In this connotation, rights can be either negative or positive.
A negative right states that I, as a person better off in life, shouldn't prevent people for acquiring their needs, but I also have no moral obligation to help those worse off than me.
A positive right demand that if someone finds himself unable to acquire his needs, he is entitled to get help to do so. Here a right becomes an obligation. You, as a moral, self-aware creature, have a duty to help others regardless of your personal stake in the matter.

Obviously, Justice is just about stuff. It's also about doling punishments to wrongdoers. People generally have varying opinions on how punishments ought to be handled, which I will list and you can look up for a deeper understanding.
1. Retributive Justice: Wrongdoers should suffer in proportion to how much they made others suffer. In other words, the classic biblical notion of 'an eye, for an eye'.
2. Welfare maximisation: Needless punishment does no good. Instead ideas such as rehabilitation or deterrence are more preferred.
3. Restorative Justice: Wrongdoers must make amends for the actions they have done. This is the basis for the idea of social service.

In summary, Justice is important because it shapes how our social world works. And as American political philosopher Micheal Sandel said ''Justice is inescapably judgemental. Questions of justice are bound up with competing notions of honor and virtue, pride and recognition. Justice is not only about the right way to distribute things. It is about the right way to value things.''