(Capcom's primary storyline)
V-JOLT (also known as V-JOLT) is an Umbrella-made chemical. It's a distinctively brown liquid, and was created when infected plants showed that certain cells would die when reacting with certain chemicals.
The V-JOLT was used by survivors of the Raccoon City Destruction Incident, who hid in the NEST. They made the chemical to destroy a mutant plant in order to reach the exit. The chemical is also used by Jill Valentine, Chris Redfield or Rebecca Chambers to weaken the Plant 42 in the Dormitory during the Mansion Incident.