Answer:
In the first past the post system, as the name implies, the party or candidate winning the a plurality of votes obtains all the political seats being contested.
For example, suppose we have three parties, and 20 seats being contested in a fictional election. The results are:
Red party - 60%
Green party - 30%
Blue party - 10%
Under a first past the post system, the Red Party would obtain all the 20 seats.
Under a proportional system, on the other hand, each party or candidate gets a proportional amount of seats corresponding to the percentage of the votes.
For example, if the number of seats contested is 20, and we obtain the same results as above, the number of seats for each party (in bold) would be:
Red party - 60% - 12 seats
Green party - 30% - 6 seats
Blue party - 10% - 2 seats
