system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: French politics. Why is there both a President and a Prime Minister. What is the point of there being a doubling up?
gpt
The president is head of state, the prime minister is the head of government. This reflects the distinction made in a constitutional monarchy with a parliament--David Cameron heads the government of the United Kingdom, as representative of the largest party in parliament, but Elizabeth II is the head of state. Most European republics with this system did so in emulation of the system they had as a monarchy.

One of the beneficial aspects of this is that the head of state is relatively stable and is not as deeply involved in politics. In a parliamentary system, the cabinet can lose power if it loses the support of a majority of parliament. If you look at the United States, an example of a presidential republic, this is not a factor because the president holds his position for a full term except in case of misbehavior. 

Imagine the nonsense that would occur if Congress could unseat the president and call a new election. It'd be terribly inconvenient, particularly on the international level. A system with separate head of state and government allows for a consistent leadership while retaining the traditional tight control of parliament on the cabinet ministers.