Mass of a substance is a measure of the amount of matter contained in that substance. It is an extensive property and varies with changes in the quantity of a substance. In simple terms, higher quantity of a substance has more mass as compared to lower quantity of the same substance. It is measured in kilograms or grams, etc.
Volume is a measure of space occupied by a substance. It is also an extensive property of matter. It is measured in liters, milliliters, etc.
Density of a substance is the ratio of its mass to its volume, that is
Density = mass/volume
It is an intensive property of matter. In other words, increase in the quantity of a substance does not increase its density. It is measured in kg per cubic meter or grams per milliliters, etc.
Hope this helps.
density is same as mass when volume is equals 1