Okay kiddo, have you ever used Google Maps to find directions to a place? Just like that, the United Kingdom has its own version of Google Maps in space called a Global Navigation Satellite System (GNSS).
Think of it like this: the GNSS is made up of a bunch of satellites orbiting the Earth that send out signals to different devices such as phones, cars, and airplanes, to help them navigate and know where they are on Earth.
The UK decided they wanted their own GNSS, so they created one called the UK Global Navigation Satellite System (UK GNSS) or sometimes called "OneWeb". The UK GNSS is still being developed and will work similarly to GPS (which is the GNSS made by the United States).
The goal of the UK GNSS is to make it more accurate and reliable for people in the UK to use, especially for things like driving, flying, and even using drones. It's like having your own special map that only you and your friends can use.
So, that's the UK GNSS! A special satellite-based system that helps people in the UK know exactly where they are and where they are going.