A trademark is considered descriptive if it merely describes the goods/services the brand offers. Moreover, a descriptive trademark might describe the quality of a product or a service, its' content or ingredient, feature, or characteristic. For example, the brand name "Fizzy and bubbly" for a soft drink would is considered descriptive, as it directly describes the quality of a given product.
Generally, you cannot trademark a descriptive brand name or a product name. However, there might be some exceptions where you can establish a so-called "distinctiveness earned through use" or "acquired distinctiveness". If you have been doing business for over five years and the public associate certain goods and services with your brand, you might be able to register your brand name. If you wish to do so, extensive evidence is needed to prove that this is the case.