What is First Past the Post and why has it been criticised?

First Past the Post is an electoral system used in countries such as the USA and the UK to elect representatives. It works in a very simple way: the candidate who recieves the most votes wins. So, for example, lets say that Candidate A recieves 25% of the vote, Candidate B recieves 30% of the vote, Candidate C recieves 32% of the vote, and Candidate D recieves the remaining 13%. Candidate C will be elected, even though he has secured less than half of the votes. 

Critics of the system would point out that this is unfair, as it leads to the majority of people not getting their desired result: 68% of people voted against Candidate C, yet he still wins. When this is applied to every seat it can be hugely disproportionate. In the 2015 General Election in the UK, the Conservative Party secured 38% of the vote, but because it came first in over half of the seats in the country, it secured a majority: 331/650 seats. On the other hand, UKIP secured 12% of the vote, but because it only came first in one seat, it only won that one seat.