There are various types of proportional representation, but if you are doing work about the system that they used in Weimar Germany it's best to stick just to that one, I think.
It's a bit difficult to understand for people in the UK because we don't/never have use(d) a system of proportional representation. What we use when voting for Members of Parliament (M.P.s) is called the 'first past the post' system whhich means that the candidate (person representing a Political Party) who gets the most votes in his/her constituency (voting area) is elected even if they only get one more vote than any other candidate. This has the advantage of being nice and simple and it (more importantly) means that normally one Political Party will be a clear winner in the General Election and therefore will be able to form a government that is able to get a clear majority in Parliament for the laws and policies it wants to introduce. The big
disadvantage of this is that smaller Political Parties may get lots of votes in the election but only end up with a few seats in Parliament (because they just lose in lots of different constituencies). So for example, the Liberal Democrats in the UK now have a lot of support in some parts of the country, but they don't have very many seats in Parliament.
This is where 'proportional representation' comes in. Unlike the system I have described above what they had in Weimar Germany was a system where people voted for a
list of candidates (eg. Social Democrats, Communist, Nazi etc) and then the seats in the Reichstag (Parliament) were allocated according to the
proportion of the total votes that each political party had got. So .... if a Party got 20% of the votes they got 20% of the seats, 40% of the votes = 40% of the seats and so on.
I hope that's clear?
The main advantage of this is that it's a
fairer system than the one we have in the UK because even a small political Party will get
some representation in Parliament. The big disadvantage is that this system often encourages the formation of lots of small Parties (with very little difference in ideas between some of them) and it also often means that no one Party gets a clear majority. As a result of this it makes it hard for one Party to form a government on their own so they are forced to make a 'coalition' (sort of alliance) with one or more of the other Parties .... and that can make it hard to get agreement about what policies to follow and what action to take.
.... and that is what tended to happen in Weimar Germany.
I hope that helps?
If you want/need to find out more about the Weimar system of government in general then see this page (it's for AS students):
http://www.schoolshistory.org.uk/ASLevel_H...onstitution.htmor this one for GCSE students:
http://www.historylearningsite.co.uk/weicons.htmor this one for GCSE:
http://www.johndclare.net/Weimar2.htmHowever, none of these explain proportional representation in as much detail as I have done .... and this is why I gave a lengthy answer.