A. Additives are used to extend shelf life or make a food more convenient or attractive or to be lower in kilojoules/calories. There are around 300 additives permitted for use in Australia and you can group them into around 20 different categories based on what function they perform.
On food labels, you'll find additives often listed under this functional name plus a code number eg. sulphur dioxide is commonly used to kill off unwanted bacteria and to prolong the life of wine and must be listed as on the bottle as PRESERVATIVE (220) or else as PRESERVATIVE (sulphur dioxide).
Here's the list of these functions: