Often it can be killed with a bit of soap and warm water or some disinfectant. Inside a living organism, it's a different story. To get an idea of the difference, think of a battery. All by itself it's just a lifeless piece of metal filled with acid. Similarly, viruses are activated inside a host body.
Some viruses are harmless.
Others can cause temporary colds or flu. But HIV can be deadly. That's partly because of the home it chooses in the human body, the t-cells that help make up the body's defense against disease, the immune system. T-cells are just one of many types of white blood cells that work together to kill any germs that invade the body. In a healthy immune system, the t-cells act as guards.