Clinical trials involve testing new drugs and treatments on humans to evaluate safety and efficacy. They are conducted in phases, starting with small groups and progressing to larger groups. Prior to conducting clinical trials, approval must be obtained from regulatory authorities like the FDA or DCGI. Trials must abide by ethical guidelines like the Declaration of Helsinki, which require minimizing risks and obtaining informed consent. The document outlines the various phases of clinical trials and legal requirements for conducting trials in India, including obtaining necessary permissions and following guidelines on ethics committee approval and compensation.