Avogadro's number represents the quantity of atoms in exactly 12.00 g of carbon-12 and corresponds to the number of atoms, molecules, ions, formula units, or other particles present in one mole of any substance.

That is correct. Avogadro's number, also known as Avogadro's constant, is a fundamental chemical constant that is the number of particles (such as atoms, molecules, or ions) found in one mole of a substance. It is named after the Italian scientist Amedeo Avogadro. The value of Avogadro's number is approximately \(6.022 \times 10^{23}\) particles/mole. This means that in one mole of any pure substance, there are roughly \(6.022 \times 10^{23}\) particles of that substance.

To relate this to the example you mentioned:

If you have exactly 12.00 g of carbon-12, which is the isotope of carbon with an atomic weight of 12 unified atomic mass units (u), this mass contains Avogadro's number of carbon atoms. - The reason this particular mass is chosen is that the atomic weight of carbon-12 is defined as exactly 12 u, and by definition, the mass in grams of one mole of a substance (its molar mass) is numerically equal to its atomic or molecular weight in unified atomic mass units. - For carbon-12, a mole is 12.00 g, and that corresponds to Avogadro's number of atoms.