What is the society?

A society is a group of individuals involved in persistent social interaction, or a large social group sharing the same spatial or social territory...

Why do we need rules that everyone must obey? In short, what is the purpose of law ?

 If we did not live in a structured society with other people, laws would not be necessary. We would simply do as we please, with little regard for others. ... Even in a well-ordered society, people have disagreements and conflicts arise. The law must provide a way to resolve these disputes peacefully. If two people claim to own the same piece of property, we do not want the matter settled by a duel: we turn to the law and to institutions like the courts to decide who is the real owner and to make sure that the real owner's rights are respected. We need law, then, to ensure a safe and peaceful society in which individuals' rights are respected.

The Legislativ power

Legislative power" is a distinctly modern conception which presupposes a modern understanding of "law." In medieval Europe the authority of laws was variously attributed to God, nature, or custom; human authorities "found" or "declared" or enforced the law but were not thought to create it. ... legislative power "Legislative power" is a distinctly modern conception which presupposes a modern understanding of "law." In medieval Europe the authority of laws...

The Executive Power

The executive is the branch of government exercising authority in and holding responsibility for the governance of a state. The executive executes and enforces law. In political systems based on the principle of separation of powers, authority is distributed among several branches (executive, legislative, judicial)—an attempt to prevent the concentration of power in the hands of a single group of people. In such a system, the executive does not pass laws (the role of the legislature) or interpret them...