Products that are designed to control a specific pest - for example antimicrobial products that kill microorganisms or insecticides for use against bugs - are regulated in the United States by the Environmental Protection Agency (EPA).
These are called "registered products" and include a wide variety of items such as disinfectants, antibacterial cleaners, insecticides and repellents.
Registered products include one or more "Active Ingredient" - the substance that controls the specific pest - as well as inert ingredients such as stabilizers, propellants, fragrance or other items that complete the formula.
To be as clear as possible about registered products, as well as consistent with government requirements, descriptions of registered products within this site use the format you see above. The active ingredient is listed at the top, with the other (inert) ingredients below.
Always remember that registered products are designed for specific and important uses. It's against the law to use a registered product in a way that's inconsistent with the label.