The difference between a presidential system and a parliamentary system lies primarily in the separation of powers. In a presidential system, the president serves as both head of state and government, elected separately from the legislature. This can lead to a more direct mandate from the electorate. In contrast, a parliamentary system combines the executive and legislative branches, where the prime minister is typically drawn from the majority party in the legislature, fostering closer coordination but potentially less accountability. Each system presents distinct advantages and challenges for governance and representation.