Question: how many molecules are in 2.0 moles of hydrogen gas?
Answer: If I have 6.022×1023 H2 molecules, I have a mass of 2 gram of hydrogen molecules. If I have 6.022×1023 C atoms, I have (approximately!) 12 grams. The mole is thus the link between the micro world of atoms and molecules, and the macro world of grams and litres, the which we can easily measure by mass or volume.