COVID-19:
COVID-19 is the disease caused by the SAR-COV-2.

SARS (Severe Acute Respiratory Syndrome):
A condition that is a transition from an illness created by a Cornona Virus where the patient suffers a fever and cough. If untreated it can lead to bronchitis and pneumonia. SARS is rather rare, but can lead to lethal outcomes if left untreated.

Pandemic:
Where something has spread through a national or global standard. In viral terms it is something that can be found in most locations of a nation and/or world, but has not reached critical mass (where it has infected most of the population). Critical mass is often referred to as a widespread epidemic in the medical world.

How lethal is SARS-CoV-2?
The virus alone is not very lethal. However, it has shown to lead to COVID-19. COVID-19 can be very dangerous to certain groups of people. The media is stating that this is dangerous to the elderly, this is not entirely accurate. The elderly tend to have the conditions that can make COVID-19 lethal, but as a group are not in danger.
The conditions found were first found in the fatalities in China. Most of these were older men that had heart conditions and were heavy smokers. This along with data in Washington State (United States), Europe, Vietnam, and other regions have shown certain conditions that can put people at risk. Those with respiratory conditions or afflictions (Chronic Pneumonia, Smoking, Asthma), those with heart disease, diabetes, cancer (those undergoing radiation or chemo), and those with immunity conditions (Lupus and other auto-immune conditions included).
What makes COVID-19 lethal is that it can lead to severe bronchitis and pneumonia. These two factors can lead to organ failure and even death. COVID-19 to roughly 85 to 90% of the population is largely harmless. It will affect most like the common cold with a slightly elevated fever with a less than 1% lethality. For 9 to 15%, it will pose as a moderate cold that can cause shortness of breath, a fever, and a lethality that so far is less than 5%. For those that meet the conditions above this can be a really dangerous virus and has shown to have a lethality that can reach as high as 15% if medical treatment is not presented for the bronchitis and pneumonia that will likely arise.

What makes SARS-CoV-2 So Scary?
The lethality tied to this virus as a whole is very low compared to other pandemics experienced in the past two decades alone. The SARS outbreak of 2003/2004 had a very low contagious value, but had a fairly high lethality level. SARS-CoV-2 is exactly the reverse for most of the population base on the initial data presented by the medical communities.
The scare in SARS-CoV-2 is that it is among the most contagious viruses encountered in the modern age. People are trying to keep away from people with this virus, but it isn't the person alone that is contagious. In normal humidity (20 to 40%) SARS-CoV-2 has shown to have an area of effect of roughly 1 meter (about 3 feet) around the infected person. This also includes areas where the person has been. The virus has shown to exist in humidity (not just droplets) for hours in possibly even days. This makes this a very contagious air borne virus. It is very likely to infect virtually all the population due to how wide spread it already is.