Marijuana is the most used drug in the United States after alcohol. It's a psychoactive drug that comes from the cannabis plant. THC is the compound found in the plant responsible for the "high" the user feels when using the substance. There are different drugs produced from this plant.
Marijuana is the most common form. It is a mixture of dried flowers, leaves, stems, and seeds of the cannabis plant, usually green or grayish. The potency and quality can vary. It primarily smoked (joints, blunts, bongs), but someone can also eat it by infusing it in drinks or foods.
Hashish or hash is a concentrated form of THC. It is made from the resin of the cannabis flowers. In terms of active ingredients, it is essentially the same as marijuana, so its effects are very similar. It also comes in oil form. These can be eaten (edibles), vaped, smoked (by mixing it with marijuana, tobacco, etc.), vaped, or "dabbed" (specific method to create a cannabinoid vapor).
Synthetic cannabinoids are human-made chemicals that are similar to marijuana. They are usually smoked, vaped, or brewed in tea. People sometimes advertise them as "100% natural"; this is a false statement as they are synthetic. They are often called synthetic marijuana and are marketed as being the same as marijuana. They are, in fact, very different from marijuana. Although the ingredients act on the same receptors that THC does, the effects can be unpredictable and dangerous. Since they are unregulated, they are not necessarily safe and can be much more potent than marijuana.
Some of these synthetic cannabinoids' brand names include K2, Spice, Joker, Blaze, Demon Passion