An aurora is a natural light display in the sky especially in the high latitude (Arctic and Antarctic) regions, which is caused by the collision of energetic charged particles with atoms in the high altitude atmosphere (or thermosphere).
The charged particles originate in the magnetosphere and solar wind and, on Earth, are directed by the planet’s magnetic field into the atmosphere.
Aurorae are classified as diffuse and discrete. The diffuse aurora is a featureless glow in the sky that may not be visible to the naked eye, not even on a dark night. It defines the extent of the auroral zone.
The discrete aurorae on the other hand are sharply defined features within the diffuse aurora that differ in brightness from just barely visible to the naked eye, to bright enough to read a newspaper by at night.
In northern latitudes, the effect is known as the aurora borealis (or the northern lights). Its southern counterpart, the aurora australis (or the southern lights), has features almost identical to the aurora borealis and changes simultaneously with changes in the northern auroral zone.