A Word Mark is a Trademark that make the name of the organization the primary component of the Trademark. Most people thinks a “Trademark” is the graphical element or icon that accompanies the name. But the true definition of the Trademark is the symbol and the name together in a cohesive unit. With a Word Mark, that primary graphical element is eliminated and the design focuses on the stylized presentation of the name itself.
Just because the “primary” symbol element is missing, does not mean that the Trademark is “plain text”. Often the stylized name is accompanied by other graphic elements, they just are not the primary focus of the Trademark.