The difference between a parliamentary and a presidential system of government lies primarily in the structure and functioning of the executive branch. In a parliamentary system, the executive is derived from the legislative branch, meaning that the head of government (usually a prime minister) can be removed by a vote of no confidence. Conversely, in a presidential system, the president is independently elected and holds significant powers that are separate from the legislature, typically serving fixed terms. This fundamental distinction affects how policies are proposed, debated, and enacted.