The mission of NIDA is to advance science on the causes and consequences of drug use and addiction and to apply that knowledge to improve individual and public health.
https://www.psychologytoday.com/us/basics/addiction
A person with an addiction uses a substance, or engages in a behavior, for which the rewarding effects provide a compelling incentive to repeat the activity, despite detrimental consequences. Addiction may involve the use of substances such as alcohol, inhalants, opioids, cocaine, and nicotine, or behaviors such as gambling.