A molar, often represented by the symbol "M," is a unit of concentration used in chemistry to express the amount of a substance in a solution. Specifically, it measures the number of moles of solute per liter of solution. One molar solution contains one mole of solute dissolved in one liter of solvent, making it a convenient way to quantify concentrations in chemical reactions. The concept of a mole is fundamental in chemistry, as it allows scientists to relate the mass of a substance to the number of particles it contains, such as atoms or molecules. This relationship is crucial for understanding reactions and stoichiometry, which involves the calculation of reactants and products in chemical equations.