In the British parliament, there are 650 Members of Parliament or MPs. Each MP represents a constituency, which covers an area of the country. The people of each constituency vote at a general election or a by-election to choose one person to represent them in the House of Commons. Usually, the people choose someone who belongs to a political party. When all the parties get together, the party or coalition with the most members is the government and runs the country. The leader of that party is called the Prime Minister. 