Britain's first-past-the-post voting system means that to become an MP, a candidate simply has to win more votes than any rival in their area, not a majority of votes cast.
Advantages of first-past-the-post system
Voters can change the way a country is run by voting in a government from a completely different party.
Voters can choose a politician, who they might trust as a person, as well as a party.
A single ruling party makes a strong government. MPs are able to make clear decisions on how to run the country, without having to compromise too much.
Criticisms of the first-past-the post system
A party can become the government with a minority of votes (but a majority of seats).
Some people's vote could be seen as wasted (if they want to vote for a party which is very unlikely to win the seat in their constituency).
Many people don't have an MP from their preferred party to represent their views in the Houses of Parliament.