First Past The Post Explained

There are not many countries that use the same 'First Past The Post' system of voting in the Government as the United Kingdom, but it does seem there is some confusion over who exactly we vote for.
There are 650 constituencies in the United Kingdom and on May 7th it is not David Cameron, Ed Milliband or Nick Clegg that we vote for but whoever is representing their party in that area.
For example, in the constituency of Newtown there is Mr Red (Labour), Mr Blue (Conservative) and Mr Yellow (Lib Dems) and you vote for one of these and the person who receives the most votes, Mr Yellow for example, is therefore elected and become the Member of Parliament to represent the people of Newtown in the House of Commons.  
Because Mr Yellow won, that counts as 1 MP for the Lib Dems.
In the neighbouring constituency of Oldtown, the Conservative representative wins and the score is now Lib Dems 1, Conservatives 1 and Labour 0.
This goes on all around the UK and at the end of the night, when all the winners of the constituencies is counted up, the party that has the most MP's is the winner and the new Government.
The First Past The Post name comes from the way that if one party reaches 326 MPs (out of the 650), they cannot be beaten so the post is the magic number of 326 MPs.
If the Conservatives win then they become the Government and because David Cameron is the leader of the Conservatives, he becomes Prime Minister, if Labour win Ed Miliband is the PM and if the Lib Dems triumph then Nick Clegg.
What it all means is that when you vote you are not directly voting for who you want to be Prime Minister but who you want to represent you in the House of Commons and by consequence of that, deciding who become the Prime Minister.
If, as happened in 2010, nobody reaches the 326 then some of the parties can join together and pool their members of Parliament into a coalition party to reach the 326 figure and looking at the latest polls, that could happen again this time around also.
The problem arises when you have a good representative who is great for where you live but happens to be from one Party (eg Lib Dems) but you would prefer the Prime Minister to be from another (eg Conservatives) but that is up to your conscience and the ballot paper what you consider is more important, who runs the country or who is making the decisions in your local area.