People participate in clinical trials for many reasons. Participants generally fall into two categories: Healthy volunteers and Patient volunteers.
Healthy volunteers, or people without known health issues, participate in clinical trials to test a new drug, device, or procedure for the benefit of others. These participants get the satisfaction of helping researchers move science forward and improve our understanding of how best to treat diseases. Participants are almost always paid for participating too. For example, clinical trials of vaccines -- including the trials for Covid-19 vaccines -- involve healthy volunteers.
Patient volunteers, or people with known health issues, participate in clinical trials to better understand, diagnose, treat, or cure those diseases or conditions. These participants take part to help others, but also to potentially access the latest experimental treatments and to benefit from additional care provided by clinical trial team members.