In NZ, the presence of sulphur dioxide is required to be noted on the label. Sulphur is produced naturally from the grapes through the fermentation process, so all wines will contain a certain amount. The other way you'll encounter sulphur is in its addition as a preservative, used to inhibit oxidation and microbial spoilage. The amount used varies, and therein lies the difference: between those who adhere to the formulaic approach and those who do everything they can to reduce their sulphur content. Some wines have no sulphur added at all.