The Convention on the High Seas is like a set of rules that all the countries around the world follow when they are on the big part of the ocean that does not belong to any one country. Just like when you go to the playground and there are rules to keep everyone safe and happy, the Convention on the High Seas has rules to make sure that countries' ships and people who are on the ocean follow certain things so there are no problems.
One rule is that everyone should be nice and friendly to each other. Just like when you meet someone new and you say "Hello" and "Please" and "Thank you," countries should also be polite. They should not hurt each other or do anything that would make the other country's people feel scared or sad.
Another rule is that countries are not allowed to take things from the ocean that are not theirs. Just like you might have toys that belong to you, the ocean has things that belong to it like fish and plants. Countries should not take too many fish or hurt the plants because that could hurt the ocean and the animals that live in it.
Also, countries have to be careful not to hurt each other's ships when they are on the high seas. Just like when you are riding a bicycle and you have to watch out for other people on their bicycles so you don't crash into each other, countries have to watch out for each other's ships. They should not crash into each other or do anything that would damage the ships or hurt the people on them.
Lastly, if someone is in danger on the high seas, all the countries have to work together to help them. Just like when you see someone who is hurt and needs help, you go and get an adult or call for help, countries should do the same. They should help each other if there is a shipwreck or if someone is lost or needs medical help.
The Convention on the High Seas is important because it helps make sure that everyone is safe and that the ocean is protected. Just like the rules you follow at school or at home help keep you safe and happy, the rules of the Convention on the High Seas help keep countries and people on the ocean safe and happy too!