how does cannabis stimulate the mind and affect people differently?

Cannabis, also known as marijuana among other names, is a psychoactive drug from the Cannabis plant. The cannabis plant has been used as a drug for both recreational and entheogenic purposes and in various traditional medicines for centuries. But  who discovered cannabis? what is delta-9- tetrahydrocannabinol(THC)? where is this drug mainly consumed? when did it become popular in society? why do people take this drug? what makes this drug so addicting?