The Gauss-Krüger coordinate system is a way for people to pinpoint locations on a map based on their longitudes and latitudes.
Think of a map as a piece of paper with lines drawn all over it to represent the globe. The latitude lines are horizontal and measure how far north or south a location is from the equator. The longitude lines are vertical and measure how far east or west a location is from the Prime Meridian (the imaginary line that goes from the North Pole to the South Pole and passes through Greenwich, England).
In the Gauss-Krüger system, these lines are divided into smaller sections and given numbers to make it easier to find specific locations. Instead of saying a location is at 42.5 degrees north and 72 degrees west, we might say it's in the section labeled "zone 18T" or something similar.
This system is used by cartographers (people who make maps) to make sure their maps are accurate and easy to use. It's also used by GPS devices and other navigation systems to help us find our way around the world. So the next time you use a map or GPS, remember that there's a whole system working behind the scenes to make it all possible!