Think of banish as when you have a toy that keeps making a loud noise and you need some peace and quiet. You might put that toy in a different room so it doesn’t bother you anymore. That’s a bit like banishing the toy; you’re sending it away to another place.
Another way to understand banish is like when you have a big, scary shadow in your room at night. You might turn on a light or ask someone to help you so the shadow goes away. When the shadow disappears, it’s like you banished it.
Imagine you have a box of crayons, and one crayon is broken and doesn’t color well. You might decide to take that crayon out of the box so it doesn’t cause any trouble when you want to draw. That’s like banishing the broken crayon from your box.
Banish can also be like when you’re playing in the sandbox and someone keeps throwing sand. You might ask them to play somewhere else so everyone can have fun without getting sand in their eyes. Asking them to play somewhere else is banishing them from the sandbox.