Cannabis extracted from the Cannabis plant contains hundreds of different ingredients. One of the ingredients is Tetrahydrocannabinol, THC, which is responsible for the high which cannabis users experience. The use of THC is regulated in many countries.
Another popular ingredient in cannabis is Cannabidiol, or CBD , which does not have any properties which are psychoactive , and has been proved to have medicinal properties.
So in many countries, CBD oil extracted from Cannabis is used for treating a number of health problems like epilepsy which cannot be cured using other methods.