Someone who is scatterbrains is not very good at focusing or remembering things.
Being scatterbrains is usually not a good thing because it can make it hard to get things done.
Examples:
She is such a scatterbrains, always forgetting where she put her toys.
The scatterbrains couldn't remember where he left his snack.
The little scatterbrains lost his favorite book again.
I'm such a scatterbrains, I forgot to bring my lunch to school today.
He's a real scatterbrains, he forgets everything all the time.
The scatterbrains couldn't even remember his own name.