Imagine you are at the beach playing with sand and water. Sometimes, the water level goes up and sometimes it goes down. Otranto Barrage is like a big wall that blocks the water from going back into the sea. It is not made of sand, but instead it is made of big concrete blocks.
The Otranto Barrage wall was built in a place where the sea joins to a big lake. The lake needs water to survive, so the Otranto Barrage wall only stops the water when there is too much of it. When the water level is too high, the Otranto Barrage stops it from flooding the surrounding area.
It is important because the lake is used for important things like fishing and tourism. So, the Otranto Barrage wall is like a giant guard that helps keep people safe from flooding and keeps the lake full of water so people can enjoy the many benefits it provides.