GPS stands for Global Positioning System. It is a network of satellites that orbit the Earth, and they are used to help us figure out our exact location on the planet.
GPS satellites send out signals that your GPS receiver, like the one in your car, can pick up and use to figure out where you are. But, if there are too many things blocking the signals from the satellites, then your device might not be able to pick up the signal. That's why it's important to know about GPS satellite blocks, because if you have too many things blocking the signal, then your GPS won't be able to accurately tell you where you are.