A coronal mass ejection, or CME, is a burst of solar winds, plasma and magnetic fields released into space. CMEs are sometimes associated with solar flares and other activity. If a CME reaches Earth, it's referred to as an interplanetary CME. On Earth, such activity can interrupt radio communications and damage satellites and electrical transmission lines.
CMEs reaching Earth can also produce strong auroras around Earth's magnetic poles, known as the Northern and Southern Lights.
Read more on coronal mass ejections.