Clinical research (or clinical trials) is one of the final stages of a long and careful research process. Researchers test new types of medical care, which helps doctors and researchers see if the new care works and if it is safe. Clinical trials may also be used to compare different treatments for the same condition to see which treatment is better, or to test new uses for treatments already in use.

References

https://www.medicare.gov/coverage/clinical-research-studies
https://www.cms.gov/apps/glossary/default.asp?Letter=C&Language=English