Generally used to describe the amount of a substance, volume is most commonly used to express measurement of solid or liquids. It is also used to express the amount of solid or liquid that can fit into a certain space. For example, the size of the boot / trunk of a car.
The base unit for volume in the International System of Units (SI) is the cubic meter (m³) and represents an amount of substance that would equal the size of a perfect cube measuring 1m on all sides.
Due to such common, early and various use, volume is the property with one of the largest number of different units. From building materials (board feet - FBM) to compressed gas (litres - L) and cups of sugar (cups is a unit!) to a swimming pool of water (m³) , the world of volume is probably the most confusing of them all.
Combine this with the ongoing issue of different countries adopting different systems, the need for and easy way to convert volume has never been more important.