The distinction between a presidential system and a parliamentary system of government lies in the structure and separation of powers. In a presidential system, the president serves as both the head of state and government, operating independently of the legislative body. This separation allows for distinct powers and responsibilities but can lead to conflicts or gridlock. In contrast, a parliamentary system combines executive and legislative functions, with the prime minister emerging from the elected legislature. This system facilitates collaboration between branches but can also create instability due to coalition governments. Each system has its advantages and challenges, shaping governance dynamics in different ways.