Proportional representation (PR) is a voting system in which political parties are awarded a number of seats in proportion to the number of votes they receive. This means that parties with a small share of the vote can still win representation in the government. PR systems are typically used in multiparty systems, where a large number of parties compete for votes and seats in the government.
First-past-the-post (FPTP) is a voting system in which each voter casts a ballot for their preferred candidate, and the candidate who receives the most votes wins the seat. FPTP systems tend to produce two-party systems, where only a few parties have a realistic chance of winning elections.
One reason why PR systems tend to produce multiparty systems is that they allow for a more diverse range of viewpoints to be represented in the government. Since parties with a small share of the vote can still win seats, it is possible for a variety of smaller parties with different ideologies to gain representation. This can lead to a more diverse and representative government.
In contrast, FPTP systems tend to produce two-party systems because they tend to favor the largest parties. In FPTP elections, voters who support smaller parties may feel that their vote is wasted if the party does not have a realistic chance of winning. As a result, they may choose to vote for one of the larger parties instead, leading to a concentration of support for the two largest parties. This can make it difficult for smaller parties to gain representation and can lead to a less diverse range of viewpoints in the government.