A trademark is a source indicator of goods or services. As such, you want your mark to stand out and be remembered. There are types or categories of marks that provide a greater level of protection than others. The types in order of strength (most to least) are: arbitrary, fanciful, suggestive, descriptive and generic.
Marks with the greatest scope of protection are arbitrary ones. These are marks that consist of made-up words created specifically for use as a trademark. These include Kodak and Exxon. These marks have wide protection because all association with the mark is in connection with the owner’s product and/or service. Fanciful marks are actual words that are used in connection with a completely unassociated product or service. A good example of a fanciful mark is “Apple” for computers. Suggestive marks are words that have been selected because they are suggestive of a particular attribute or feature of the product or service. Suggestive marks would include “Jaguar” automobile, or “Greyhound” bus service. Arbitrary, fanciful and suggestive marks are essentially acceptable for use as a trademark or service mark barring any third party uses.
Descriptive marks are more difficult to protect because they describe the product or service. The US Trademark Office will reject an application for a trademark that is “merely descriptive” of its goods or services. If your mark merely or only describes the goods or services, you may have a difficult time obtaining trademark registration for it. However, a mark is entitled to trademark registration as a descriptive mark if it is not merely or solely describing the goods or services. This requires proof of distinctiveness or “secondary meaning”. Distinctiveness is obtained when consumers associate the mark with the goods or services. “Best Buy” for retail stores selling electronics and appliances is an example of a descriptive mark. Finally, generic marks are marks that become what we use as a noun for a product or service. Examples of trademarks that have become generic include escalator and linoleum. Generic marks have no protection because they no longer are a source indicator. Trademark owners need to walk a fine line between obtaining the status of a well-known mark and having that mark become the generic term for the good or service sold.
If you are selecting a new mark, arbitrary, fanciful or suggestive marks are preferred (in decreasing order of preference) for providing a greater scope of protection. The type of mark does not mitigate the need to determine whether the mark is available for use based on all third party uses of the same or similar marks.