A postdoctoral position (postdoc) is not considered a higher degree than a PhD; rather, it is a stage in an academic or research career that follows the completion of a PhD.
PhD: This is a doctoral degree that involves extensive research, culminating in a dissertation that contributes new knowledge to the field.
Postdoc: After earning a PhD, individuals may pursue postdoctoral research to gain additional training, conduct further research, and publish results. It is typically seen as a temporary position designed to enhance skills and experience.
In summary, a postdoc is a professional role taken after obtaining a PhD, rather than a higher academic degree.