Short answers, pulled from the story.
Absolute monarchy is a form of government in which the sovereign holds political power unconstrained by constitutions, legislatures, or other checks on authority. Constitutional monarchies, by contrast, restrict or balance the monarch's authority through legislatures, unwritten customs, or other officials such as a prime minister.
Brunei, Eswatini, Oman, Qatar, and Saudi Arabia appear on most datasets as absolute monarchies. Some researchers also classify Bahrain, Bhutan, Jordan, Kuwait, Liechtenstein, Monaco, Morocco, Tonga, Vatican City, and the United Arab Emirates as absolute monarchies.
European absolute monarchs most commonly invoked the divine right of kings, the doctrine that their authority came directly from God and therefore stood above any human institution. The 1665 Kongeloven of Denmark-Norway encoded this in law, declaring the monarch "the most perfect and supreme person on the Earth" with no judge above them except God.
Frederick the Great adopted the title King of Prussia in 1772 and practiced enlightened absolutism until his death in 1786. He introduced a general civil code, abolished torture, established the principle that the Crown would not interfere in matters of justice, and promoted an advanced secondary education system that became the forerunner of the German gymnasium.
Russia abolished absolutism in 1905, making it the last European country to do so and the only one to abolish it in the twentieth century. The Romanov dynasty's rule ended entirely in 1918, when the Bolsheviks executed the Romanov family.
Historians such as Roger Mettam argue that rulers called absolutists often exercised no more real power than non-absolutist rulers, and that absolutist rhetoric diverged sharply from actual governance. Renaissance historian William Bouwsma pointed to the chronic financial weakness of supposedly all-powerful kings as evidence of the limits of royal power.