How do presidential and parliamentary systems differ in their structures and functions?

Presidential and parliamentary systems differ in their structures and functions primarily in how the executive branch is formed and its relationship with the legislative branch. In a presidential system, the president is elected separately from the legislature and holds significant powers, while in a parliamentary system, the executive branch is formed from the legislature and the prime minister is typically the leader of the majority party. Additionally, in a presidential system, the president has a fixed term and cannot be easily removed by the legislature, whereas in a parliamentary system, the prime minister can be removed through a vote of no confidence by the legislature.