Define mole. Give its symbol. What is the advantage of this mole concept?

(N/A) mole of particles (atoms,ions,or molecules) is defined as the amount of a substance that contains the same number of particles as there are in $12 \ g$ of the $C-12$ isotope.
Experimentally,it has been found that $0.012 \ kg$ of carbon-$12$ contains $6.022 \times 10^{23}$ atoms. This number is called Avogadro's number or Avogadro's constant and is represented by the symbol $N_A$ or $N_0$.
The symbol for the unit of mole is $mol$.
Advantage of the Mole Concept:
The mole concept allows for the convenient selection of a specific number of atoms and molecules by relating them to the mass and volume of a chemical substance,making stoichiometric calculations easier.