Service marks, certification marks and collective marks are regularly called "trademarks." Each of these categories of marks contain wordmarks and design marks. A wordmark does not contain a logo or design. It is simply the word being claimed as a trademark. A design mark contains the logo or design of a mark. For instance, "Nike" is a wordmark. The Nike "swoosh" is a design mark. Both wordmarks and design marks are protectable under trademark law. Getting federal trademark protection on your company's wordmark does not mean your design mark is protected. Getting protection on your design mark does not mean your wordmark is protected. You would need to register both to protect both.
One design mark might be confusingly similar to another design mark but the wordmarks of the two might be dissimilar. Likewise, a wordmark might be confusingly similar to another wordmark but the design marks of the two might be dissimilar.