Raoult's Law states that the vapor pressure of a solvent in a solution is directly proportional to the mole fraction of the solvent present. This means that as the concentration of the solvent increases, its vapor pressure also increases. The law applies to ideal solutions, where interactions between different molecules are similar to those between like molecules. In practical terms, Raoult's Law helps predict how the presence of a solute affects the vapor pressure of a solvent. For example, adding salt to water lowers the vapor pressure, which is important in processes like boiling point elevation and freezing point depression in solutions.