What is first past of the post system
In a first-past-the-post electoral system, voters cast their vote for a candidate of their choice, and the candidate who receives the most votes wins (even if the top candidate gets less than 50%, which typically happens when there are more than two popular candidates).
FPTP is a plurality voting method, and is primarily used in systems that use single-member electoral divisions.
FPTP is used as the primary form of allocating seats for legislative elections in about a third of the world's countries, mostly in the English-speaking world.
The phrase is a metaphor from British horse racing, where there is a post at the finish line (though there is no specific percentage "finish line" required to win in this voting system, only being furthest ahead in the race).