Sulfite and sulfate are the two most common oxyanions of sulfur. They are both widely used in everyday items. You can, for instance, find sulfates, SO42-, in shampoo and toothpaste. The reason you find sulfates in these products is that they make your shampoo and toothpaste lather. As part of chemicals like sodium lauryl ether sulfate (SLES), sulfates can bind to both water and oil, which is essential for lathering to occur.
Sulfites are, on the other hand, found in many foods. Sulfites occur naturally in wine, but in other foods, we add them for the sake of preservation. Such addition is the case for dried fruit, where sulfites stop the natural browning and ripening processes.
The usefulness of sulfates and sulfites in our everyday lives is apparent, but how about the corresponding acids, sulfuric and sulfurous acid? Sulfuric acid is a strong acid and is therefore often used in chemical manufacturing. Sulfurous acid would like to convert to sulfuric acid by binding to another oxygen atom, which means it is a reducing agent. So, sulfurous acid and sulfuric acid have many applications, but we can also find them in unwanted places, e. g. as acid rain.