Answer:
Step-by-step explanation:
In a constitutional monarchy, the monarch is governed by a constitution. In the case of Great Britain, traditional heavy systems of control limit what the Queen/King can and can not do.
A parliamentary system of governance involves a parliament whose members are elected and represent their parties. The numbers of votes per party determine the ability to “form a government” and choose a prime minister. The leading party in votes need not be a part of the government formed (e.g., Finland, at present); only those parties whose agenda are enough in agreement to cooperate in parliamentary votes effectively and choosing the prime minister. A president is largely a figurehead chosen by election for a fixed term.
Now, why isn’t a question like this looked up in Wikipedia?