There are no constituencies in this system.
Voters vote for a party not an individual.
The party leaderships draw up the lists, placing their more favoured candidates near the top of the list and the less favoured candidates at the bottom.
After the votes are counted, the proportion of votes that a party has is calculated. Candidates from that party are then elected to an assembly in the same proportion i.e.
If a party gets 30% of the votes cast, the top 30% of the party’s list goes through.
A variation is the regional list system. This, rather than being a national list, is a regional list to truly reflect regional feelings. This regional list was used in the 1999 European Parliament elections held in GB.
It is almost impossible to win an election outright and countries that use this system tend to exist using coalition governments. Coalition governments are usually weak and unstable.
The system does mean that every vote counts and therefore is socially representative.