What are clinical trials?

What are clinical trials? Clinical trials are for patients who are diagnosed with a condition like leukemia or MDS. You know, for them there are different types of clinical trials. Some are observational, where we know what is the natural history of the disease. Then there are experimental, where there will be an intervention like giving a drug or testing a new therapy for either newly diagnosed patients or patients who are already on treatment and not getting an appropriate response.