Trademark Offices around the world use classes to divide commercial products and services into defined categories. When you apply for your trademark to protect your brand, you must define the class or classes that you believe best describe your business activity.
Countries around the world have standardized 45 classes (34 for products and 11 for services) for international use under the Nice International Classification.
These classes group all known products and services. If applicable, you can register the same trademark in more than one class; for example, you may register the trademark KING for computers in class 23 and register the same trademark in class 24 for cosmetics.
Trademark protection only extends to commercial use within your specified classes. It is, therefore, possible for two entities conducting business in different classes to use identical or similar trademarks and for each entity to enjoy full trademark protection in their respective classes. If you feel that protection should extend to include more than one class, you can choose multiple classes under which to conduct business.
You can search for your trademark class with this Trademark Class Search tool.