A postdoctoral fellow is an individual who has completed their doctorate degree (PhD) and is engaged in a temporary period of advanced research, often to enhance their professional skills or gain further experience in their field. They typically work under the guidance of a senior researcher or professor, conducting research projects, writing grants, publishing papers, and teaching classes within their area of expertise. The position usually lasts for one to three years depending on the funding available and is often seen as a stepping stone towards obtaining a tenure-track faculty position at a university or research institution.