Thank you for writing!
This is a very indepth and broad question.
Pain can be categorized in many ways, from chronic (long term) to acute (sudden/non permanent) to sharp pain, dull pain, throbbing pain or one could have joint pain, bone pain, muscular pain, tissue pain etc.
Pain scales are fairly simple - is your pain hardly noticeable, tolerable, intense or excruciating...
May I ask what direction you are going with your research? Are you conducting a study or research paper?
We look forward to hearing back from you!