Moles are the units used to measure the concentration of a chemical in a solution.
A mole, in chemical terms, should not be confused with a small brown furry animal that can dig up your lawn. Nor with Molarity (denoted by M) which is a measure of concentration of a chemical species/substance in moles per unit volume, commonly per litre (Mol/L).
The numbers of moles in a sample can be calculated as follows:
Number of Moles = Mass of the Sample (g) / Relative Formula (or Atomic) Mass
For example, the mass of 1 mole of sodium chloride (NaCl) is 58.44g.