A mole is just a pile of atoms or molecules. The number of particles in the pile is always to same: there are always 6.02 x 1023. This number is called Avogadro's constant.
So if I give you a mole of anything - you will be given a very large number of particles ... 6 with 23 zeros after it. You will be given Avogadro's constant number of particles. You will always get the same number of particles - but the mass of what I give you will depend on the mass of the individual particles. E.g. if I give you a mole of carbon - I'd have to give you 12 grammes of carbon. 12 grammes of carbon contains 6.02 x 1023 atoms. Probably too many to count!