what's the major differences between the three?

Basic: Sometimes "pure" or "fundamental," research designed to advance knowledge for the sake of it.
Applied: Research geared to solve practical issues.
Clinical: Research that involves patients, such as clinical trials.

In general, clinical research is a part of applied research, and applied research necessarily follows basic research. You'll get different definitions from different people, though, so nothing's black and white.

yea the main trouble I was having was differentiating between clinical and applied, because I always used the two synonymously.

I found a good website that talks about this: http://www.lbl.gov/Education/ELSI/research-main.html