This is the biggest election in the UK. It's about picking a new government and must happen at least once every five years.
The election normally takes place more often than this. That's because the Prime Minister gets to pick the exact date and by going to the polls a bit early the PM is able to keep his opponents guessing about when the vote will take place.
Everyone in the UK who is registered to vote can have a say in choosing the next government. One Member of Parliament (MP) is elected from each of the UK's 659 parliamentary constituencies.
Each registered voter gets one ballot paper. They mark it with a cross next to the name of their chosen candidate. The candidate who gets more votes than any other becomes an MP. This is called first past the post.
When the 659 MPs have been chosen, the leader of the largest group (political party) gets asked to form a government.