An absolute monarchy is a idealised form of government, a monarchy where the ruler has the power to rule their country and citizens freely with no laws or legally-organized direct opposition telling the monarchy what to do, although some religious authority may be able to discourage the monarch from some acts.
Basically an absolute monarch has total power over its people and land - including the aristocracy. As a theory of civics, it puts total trust in well-bred and well-trained monarchs raised for the role from birth - and often terrified for their lives.
The theory of absolute monarchy developed in the late Middle Ages from feudalism during which monarchs were still very much first among equals among the nobility. With the creation of centralised administrations and armies backed by expensive artillery, the power of the monarch gradually increased relative to the nobles, and from this was created the theory of absolute monarchy.
The political theory which underlies absolute monarchy was that the monarch held their position by the grace of God and was therefore not answerable to mortals. Much of the attraction of the theory of absolute monarchy in the Middle Ages was that it promised an end to devastating civil wars and could put an end to corruption by the aristocracy, and restore attention to the Church's moral codes. Having nothing to gain but a soul to lose, the theory goes, the King was a far better figure to enforce an ethical code than social climbers or newly rich nobles.
In practice, the monarchs in absolute monarchy often found their power limited. In the 16th century, efforts by the English monarch to create an absolute monarchy led to persistent struggles with Parliament which the monarch eventually lost. In France, the monarchy was able to eventually centralise its powers and sideline Parliament and nobles. The example of an absolute monarchy is Louis XIV of France. During the Enlightenment, the theory of absolute monarchy was supported by some intellectuals as a form of enlightened despotism.
In Liechtenstein, nearly two-thirds of the tiny principality's electorate have agreed to back Prince Hans Adam's demands to become an absolute monarch; if he is successful, then Liechtenstein may become the modern world's second absolute monarchy.