Sativa vs Indica
The names indica and sativa are botanical terms used to describe the species of the plant (indica, sativa, ruderalis) and how the cannabis plant grows. Indica strains are short, stocky, “bushy” plants, and Sativa strains are typically tall and “stretchy” plants.
Sativa and Indica are commonly used to describe how a certain strain of cannabis will affect you.
Pure sativa strains are described as being energizing, uplifting, and sometimes even thought-provoking. Popular “sativa dominant” strains include citrus and piney tasting flowers such as Sour Diesel, Trainwreck, Maui Waui, Lemon Haze, Chemdog, Jack Herer, and so on.
Pure indica strains are described as relaxing, soothing, euphoric, pain relieving, and sometimes sedating. Popular “indica dominant” strains include many purples, kushes, and skunky strains such as Purple Kush, Afghan Kush, Cheese, Skunk, Grape Ape, Blackberry Kush, Northern Lights, and so on.
As most of the "old school" sativas and indicas have been bred together and crossed to make thousands of hybrids (The True OG, Blue Dream, Jillybean, XJ-13, Purple Trainwreck, and Alien OG) it is increasingly inaccurate to use the terms sativa and indica to describe the plant’s medical effects. It is really the mixture of the various cannabinoid and terpenoid compounds in the plant that determine how the strain affects you.