GCSE Chemistry Question! Please help! I have a rubbish teacher and mocks soon!!?

I am in my final year of my GCSEs and I have been given a terrible chemistry teacher.

I was wondering if anyone could explain to me what a mole is, other than a small furry animal!

Please help!

Clearest and most helpful answer gets ten points! Thanks!
Update: Okay, please NOT about small furry mammals that live underground. I mean the chemical mole!!
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