Absolutism is the principle of complete and unrestricted government power, usually in the hands of one person, a dictator or despot.
This word sounds big, but it's really just an extension of the word absolute. If you have absolute power, you control everything. The problem with this is that absolutism can survive only through dominance, threat of punishment, and violence — in other words, tyranny. And, as the British historian Lord Acton noted in 1887, "Power tends to corrupt, and absolute power corrupts absolutely."