Test pilot Hal Jordan was chosen to become a member of the Green Lantern Corps. His fearless and heroic nature have proven him worthy of the Green Lantern ring many times over, and is considered one of their greatest heroes.
The Red Lanterns are the enemy of the Green Lantern Corps. While the Green Lanterns use will for their power, the Red Lanterns use anger. When a being is possessed by a Red Lantern ring, they are transformed into raging beasts, spitting burning red energy from their mouths. Hal Jordan briefly worn a Red Lantern ring, but was saved by the Blue Lantern's power of hope.