There are over five thousand programs for post graduate study that you may elect to participate in. There are opportunities for you to take your education to another level beyond graduate or post graduate studies as well.
Many programs are available, just like graduate programs.
Requirements will vary from institution to institution. There is somewhat of a different focus than graduate studies. The programs are somewhat interdisciplinary in their focus and ultimate goal. In most cases the PhD programs lead students to become somewhat of an expert in a selected subject matter, and become proficient at navigating and utilizing the research tools to prepare for the ultimate attainment of the PhD designation. Broad understanding and the role and scope of any specific program of study is ultimately achieved, and a level of competency in the particular selected field of study is advanced.