A mole is a unit of 'amount of stuff' and is equal to 6.022x1023. It is such a big number because we use the mole to describe how many atoms we have of something, so instead of saying "I have 6.022x1023 atoms of carbon" you can say "I have 1 mol of carbon". A reminder that mole is a unit of stuff not weight so 1 mole of iron will weigh more that 1 mole of carbon as the individual iron atoms that make up 1 mole of iron is heavier than a carbon atom.