Examples of aromatics also called the BTX chemicals to include benzene, xylene, and toluene. Aromatics are the key element in types of gasoline that ultimately dictate the level of octane in the blend.
Many individuals are curious about what octane is used for.
Octane ratings, or octane number, is a standard measure of the performance of an engine or aviation fuel. -Wikipedia
In most cars, the octane rating dictates how well the car will perform. Most cars that are sold in the North American consumer market are designed to run well off of regular, or lower octane levels. The blends you see at gas stations increase in octane levels and additives like detergents. Some cars will respond favorably to higher octane levels by getting more miles per gallon and better engine performance.
The commercial fuel industry releases seasonal blends in North America. These blends alter the RVP or evaporation point. There is a great primer regarding octane ratings and RVP at Popular Mechanics RVP / Octane questions.
If your car is designed for regular gasoline you should be experiencing great performance if you stick with that level. Speak with your mechanic or car dealer about what octane your car is designed for. In most cases going up, one level may not be necessary unless you want the additives that have been blended into the product.