If you don't know what CBD oil is, you're not alone. "CBD" is short for cannabidiol, and it's one chemical compound — called a cannabinoid — in cannabis. As shown in the graphic below, cannabis doesn't just refer to marijuana. It's a family of plants. Marijuana is the type of cannabis that people are most familiar with. It has high levels of THC, which is what makes it illegal. Hemp is a different thing. It has low levels of THC and hemp has been used for centuries to make al