An extensive property is a property that changes when the size of the sample changes. Examples are mass, volume, length. If you have salt, and add more to it then the mass would change.
An intensive property doesn't change regardless of the mass of the sample. Think of intensive properties as INdependent, they don't depend on the mass of the sample. Examples are temperature, color, hardness, melting point, boiling point, pressure, molecular weight, and density. If you have one gram of salt, and on the other hand, you have 5 tons of salt, the color does not change. Because intensive properties are sometimes characteristic of a particular material, they can be helpful as clues in identifying unknown substances.