Laboratory studies
Experiments with isolated molecules or cells can help researchers investigate biological activity under controlled conditions. Those conditions differ from the complexity of a person or animal. A laboratory finding is a starting point for further investigation.
Animal studies
Animal research can investigate effects within a living organism and inform further research. The species and experimental conditions matter. Results in one species do not automatically establish the same outcome in humans or other animals.
Sources for the laboratory and animal sections: FDA, "Drug Development and Review Definitions" · National Library of Medicine, "Understanding Medical Research"
Human studies
Human studies examine outcomes in people. Their usefulness still depends on the study design, participants, size, comparison group, duration and measured outcomes. One study does not answer every question about benefit or risk.
Source: FDA, "Step 3: Clinical Research"
Research and approval are different steps
In the US drug-development process, preclinical research, clinical research, FDA review and post-market safety monitoring are distinct stages. Being studied does not by itself mean a product has been approved.
A practical reading habit
Label the evidence before summarizing it: laboratory finding, animal study, or human study. Then state what was observed and one limitation. Keep each finding tied to the substance and population actually studied.