"Division of powers" means that they separate the powers. It was important to the creation of a new government because it helped decide how their new government was gonna work out. The principle that sovereignty should be divided between the federal government and the states especially as expressed by the Constitution of the U.S.
Division of powers means splitting the powers and responsibilities of different branches of government. This is important to keep a system of checks and balances, which basically means that no single branch is too powerful.
