When you drive your car on the road, you have to follow certain rules to stay safe and avoid crashing into other cars. The same goes for big ships that travel on the oceans and seas. They also have to follow special rules to avoid getting into accidents with other ships.
One of the rules they follow is called a traffic separation scheme, or TSS for short. Think of TSS like a big road for ships, just like we have roads for our cars. This big road is divided into separate lanes going in different directions, just like how we have separate lanes for cars going in opposite directions.
These separate lanes are marked by special lines on the water and big ships have to follow them to stay in their own lane. They also have to follow different speeds in each lane, just like how cars on different lanes of a highway go at different speeds.
The main purpose of a TSS is to make sure that big ships don't crash into each other while they are traveling long distances across the ocean. The TSS helps to keep the ships at a safe distance from each other and makes sure that they don't cross paths in dangerous ways.
So just like how we follow rules on roads to stay safe while driving, big ships follow rules of TSS to stay safe while traveling on the open water.