A drug is every natural or manufactured material that affects the physical and intellectual human activity.

Drugs are divided into two types: the plant type which is used as raw material (such as marijuana) and the preparation type (such a heroin) produced in special laboratories in the form of powder or pills or liquid. Both types are characterized by containing elements that has various effects on the body, some of these dope, others activate, while others cause hallucination to the person.

Drugs can be classified as follows:

Category of sedatives: drugs such as heroin, a substance or sedative for the nervous system.

Category of stimulants: such as cocaine and crack, these are stimulants for the nervous system.

Category of hallucinogens: such as LSD, a substance that makes a person hallucinate; or Indian hemp, which if given in light doses loosens the nerves to the point of sleepiness, and if given in bigger doses leads to hallucinations. These materials are taken through different ways such as smoking or inhalation or injection. Taking these materials by injection secures the access of a bigger quantity to the brain which results in a bigger concentration and faster outcome. Besides, the use of a third of the drug quantity through injection leads to the same physical and psychological results that can be obtained when using the full amount by way of smoking or inhalation.

In addition to these categories, drugs include in its general concept: alcohol, tobacco and some industrial materials (such as pattex and type-ex) and some medicines.