Let's Talk Terpenes.
Terpenes are the aromatic compound found in cannabis and other plants. In short, terpenes are responsible for that delicious aroma that cannabis gives off - whether it be piney, diesel, or earthy - and they also have a host of therapeutic benefits as well!
Terpenes work synergistically with cannabinoids (THC, CBD, and CBN, etc.) to provide what is known as the Entourage Effect. These two compounds - cannabinoids and terpenes - work in harmony to create what we now lovingly refer to as indica and sativa strains. Terpenes are a huge determining factor in whether or not you'll experience the couch-lock body high of an indica or the alert, creative, euphoric buzz from a sativa (thanks, Pinene!)
Above is a simple guide to some of the most commonly-occuring terpenes and the effects that you may experience from each one. When searching for a strain, it's helpful to see testing so that you can determine if that particular batch will be the most effective and beneficial for your particular needs.