Okay kiddo, do you know what a canister is? It's like a container that can hold things inside.
A water canister is a special type of canister that holds water inside. It's usually made out of plastic or metal and has a lid on top to keep the water from spilling out.
People use water canisters for lots of things like when they go camping or hiking and need to bring their own water with them.
Water canisters come in different sizes so you can choose one that holds a lot of water or one that holds just a little bit. Some water canisters also come with a spout, which is like a little opening that water can come out of when you need to drink it.
It's important to make sure your water canister is clean and doesn't have any dirt or bacteria inside, so you should always wash it out before you fill it up with water.