A postdoctoral fellow refers to a post where a person who has obtained a doctorate goes to a university's scientific research site to conduct research. Some people who have finished their Ph.D. do not want to go to institutions or enterprises, or have not found satisfactory jobs. And my own scientific research results can't be an associate professor in colleges and universities, so I temporarily applied for a post-doctoral position in colleges and universities, and followed some academic giants to study unpublished thesis topics at the doctoral stage. Postdoctoral stage is the most concentrated stage for individuals to carry out scientific research, and generally speaking, doctors do research together with academic giants in various universities, which is very helpful for improving their scientific research ability. To put it bluntly, the post-doctoral position is for doctoral graduates, and I haven't found a buffer position for those who belong to my own development direction.