An epidemic is an outbreak that has spread over a large geographic area. When the outbreak spreads globally, it becomes a pandemic. A pandemic is more about how widespread the disease is and NOT how severe the disease may be.
You may have heard about the CDC alerting the country to prepare for a possible pandemic. While we need to be concerned about the possibility that the novel coronavirus will spread more widely, this news is more of a call to action than a cause for alarm, and furthermore, is an opportunity to think through what we can do to be prepared. Because we do not know yet how severe the disease may be, it is better to be over prepared than under prepared.