Some voting systems try to match the number of seats a party wins to the number of votes cast for it. This is called proportional representation.
Advantages of proportional representation
The number of MPs in the parliament is more likely to reflect the total number of votes cast per party.
It is unlikely that a party with a minority of votes can form a government.
Voters may be more likely to vote if they think it will count, so this could increase turn out and promote democracy.
Criticisms of proportional representation
Voters are less able to hold a government responsible for its actions by kicking it out at the next election.
The list system, especially a closed list, means that voters can only vote for a party, not a candidate, who they might trust as a person.
It can be harder for politicians to make difficult decisions when there is a mixture of parties sharing power in a coalition government.