Bacteria are tiny, one-celled living organisms that can only be seen with a microscope. They live and breed in warm, moist environments in the body and elsewhere, growing quickly and causing infection. They can reproduce independently, and inhabit virtually every environment on earth, including soil, water, hot springs, ice packs, and the bodies of plants and animals. Viruses are tiny geometric structures and cannot be seen with a microscope. They grow inside the body and produce toxins (poisons) that can cause rashes, aches and fevers.
Bacteria carry all the machinery needed for their growth and multiplication, while Viruses carry mainly information. Viruses are not truly "living," but are essentially information that float around until they encounter a suitable living host. Outside of a living cell, a virus is dormant, but once inside, it takes over the resources of the host cell and begins the production of more virus particles.