A doctorate degree is the highest level of academic degree in
most fields. For research or university teaching, the degree is
usually a PhD. Applied professional doctorates include the
Doctor of Medicine (MD), Doctor of Education (EdD), Doctor of
Philosophy (PhD), Doctor of Theology (Dth), and the Juris Doctor
(JD), among others.
Difference between two
degrees, such as MD and PhD are: PhDs advance knowledge and MDs
apply existing knowledge. The MD does not need to produce
original research; the PhD must produce original research and
write it up in a dissertation, which must be approved by a
review committee before achieving a PhD.
Incidentally, in the
US, a thesis is the final project for the master's degree and
a dissertation leads to a doctoral degree. A thesis is a
compilation of research that proves knowledge about the
information learned throughout the graduate program. A PhD
dissertation must contribute something completely new and
undiscovered to the field. The dissertation must contribute
original knowledge to the subject. In short, a thesis (MA)
proves someone else's point and a dissertation (PhD) proves
your own point.