Solubility refers to whether a substance will dissolve when mixed with a liquid. The liquid that does the dissolving is called the solvent, while the substance being dissolved into it is called the solute. If a substance is soluble the mixture will form a solution. If the substance does not dissolve, the mixture will form a suspension.
Salt dissolves in water, hence it is soluble in water, creating a solution of saltwater. Salt will not, however, dissolve in oil. Oil and salt will form a temporary suspension, until the salt settles to the bottom. Muddy water is another example of a suspension