Cross-sea traffic ways are like roads or highways for boats and ships to travel on across the open sea. Just like cars and trucks use roads to get from one place to another, boats and ships use cross-sea traffic ways to travel long distances and transport goods and people.
The sea can be very big and there are many different routes that boats and ships can take to get to their destination. Cross-sea traffic ways are special routes that are designated and planned to be the safest and easiest way for ships to travel between two points.
To make sure that boats and ships don't crash into each other when using cross-sea traffic ways, there are rules and regulations in place that everyone who uses them must follow. It's like when you're driving on a highway and you have to follow certain rules to keep yourself and other drivers safe, like staying in your lane and obeying speed limits.
Cross-sea traffic ways are important for trade and transportation around the world. Without them, it would be much harder and more dangerous for boats and ships to travel long distances across the sea.