All three are intended to enhance and support the academic and research development of the appointee. Individuals holding postdoctoral appointments are supervised and mentored by a senior scholar, and are guaranteed freedom to publish. Since these appointments are intended to contribute to career development, they have limited terms.
It is important to note that Postdoctoral Research Associates and Postdoctoral Research Fellows are Brown employees, while Postdoctoral Fellows are not considered Brown employees. This difference in employment status means that PDRAs and PDRFs receive salary and PDFs receive stipends; this requires different tax treatment. Moreover, although all postdocs have access to health and dental insurance through Brown, payment and withholding arrangements differ.