Okay little one, a "casco de leiro" is actually a type of traditional boat from Galicia, which is a region in the northwest of Spain. It's made of wood and has a flat bottom, which makes it perfect for navigating the shallow waters of the estuaries and rivers in the area.
The boat has a very distinctive shape, with a pointed bow (that's the front) and a wide, flat stern (that's the back). It also has a small cabin where the fishermen can shelter from the elements and store their gear. It's said that the design of the casco de leiro has remained pretty much the same for centuries, which is quite a testament to its effectiveness.
These boats are primarily used for fishing, and are known for their stability and manoeuvrability. They're also very economical, as they don't require a lot of fuel to operate, and are relatively low-maintenance.
So, there you have it – a "casco de leiro" is a lovely old fishing boat from Galicia, which is still used today. It's made of wood, has a flat bottom, and is great for navigating shallow waters. Plus, it looks super cool!