Marks which are primarily merely descriptive are not registerable on the Principal register absent a showing of acquired distinctiveness. Merely descriptive refusals can be avoided by ensuring that the applied-for mark has terms, stylization or design elements that are inherently distinctive.
A mark that has a descriptive term can still be registerable so long as the mark as a whole is not primarily merely descriptive. If a mark contains both an inherently distinctive element and a descriptive term, the trademark office will likely require the applicant to disclaim exclusive rights to the descriptive term. This does not mean that the descriptive term is not part of your mark, it simply is an acknowledgment that the term is descriptive and that you do not have exclusive rights in that term, separate and apart from how you use the term in connection with you full applied-for trademark.