General elections occur every 4 or 5 years, and elect Members of Parliament to the UK House of Commons, determining who forms the UK government. These elections are conducted using the so-called ‘First Past The Post’ voting system, whereby every registered voter casts one vote for a candidate in their town or area (known as constituencies). The candidate with the most votes wins the seat and becomes the Member of Parliament for your constituency. Their job is to represent you - and everyone in your area - in parliament.
The UK Parliament has produced a very short video describing this process:
Registering to vote is easy, and takes around 5 minutes.