An amphibious cargo ship is like a really big boat that can carry lots of things and people. It's called "amphibious" because it can go in both the water and on land.
Imagine you have a toy car that can drive in a tub of water but also on the floor. The amphibious cargo ship is like a huge version of that toy car.
The ship has a flat surface on it called a "deck" where people and things can be loaded onto it. When it's in the water, it floats like a big bathtub. But when the ship gets to a beach or shallow water, it has special ramps that can come down. These ramps allow people and vehicles to drive off the ship and onto the land.
The ship is designed to be super-sturdy so it can carry really heavy things, like tanks or trucks. It's also designed to keep people safe when they're on board and when they're going from the ship to land.
And that's an amphibious cargo ship!