Wikipedia.org defines a prepper (click me to read the entry):
A survivalist or “prepper” is an individual or group that prepares or makes preparations in advance of, or prior to, any change in normal circumstances or lifestyle without significant reliance on other persons (i.e., being self-sufficient), or without substantial assistance from outside resources (e.g. government) in order to minimize the effects of that change on their current lifestyle.
Preppers call themselves “modern-day survivalists” or “neo-survivalists” try to distance themselves from the “crazy gun nut” stereotype “survivalist”. Like survivalists, many do not identify themselves as doomers or follow the 2012 phenomenon.
Survivalists have many different mindsets and cover a broad spectrum of survival and preparedness interests. Some prepare for economic disaster or to escape genetically modified foods through organic farming or urban gardening. Some may prepare for the possibility of a complete breakdown of society while others store up extra food and water for a more localized disaster. In addition to natural disasters, terrorist attacks, as well as other crises, preppers also prepare for personal disasters and economic hardships, such as unemployment or the loss of a loved one.
Editors Note. What do you need to prepare for? Well… check the US government websites including FEMA.gov and CDC.gov.