What does a mole measure?

Hint: Mole concept is a very basic and important concept of chemistry. It relates the macroscopic amount of any substance to the number of elementary particles it contains in it. 1 mole of any substance contains $6.022\times {{10}^{23}}$ particles in it. The particles can be atoms, ions, or molecules. This number $6.022\times {{10}^{23}}$ is known as the Avogadro number and denoted as ${{\text{N}}_{\text{A}}}$.

Complete answer:
In chemistry, mole is considered a fundamental SI unit that is used to measure the amount of substance at microscopic levels. Molecules and atoms are very microscopic substances and cannot be observed or measured easily. That is why, in order to simplify the calculations, the concept of moles and Avogadro number was introduced.
Mole is the number of particles that is equivalent to Avogadro’s number $\left( 6.022\times {{10}^{23}} \right)$ . It is well defined as the amount of substance that contains the same number of molecules, atoms, or any elementary particle that is present in 12 grams of the carbon-12 isotope.
1 mole of any entity is equivalent to $6.022\times {{10}^{23}}$ number of particles. The concept of moles is a very crucial and integral part of chemistry that is mostly incorporated in calculation parts. For example, we say that 1 mole of hydrogen contains $6.022\times {{10}^{23}}$ number of hydrogen atoms and from this, we can calculate the number of hydrogen atoms present in any amount of it.
From the above discussion, we can say that mole measures the number of elementary particles such as ions, atoms, or molecules present in any amount of substance.

Note:
Mole relations are used to calculate the amount of substance in different forms. For example, the mass of a substance present in its 1 mole is known as its molar mass. Also, if we know the molar mass value, we can find out the number of moles and hence the number of atoms in any given amount of substance.