Viruses and bacteria are both tiny living things called microorganisms, but they are really different. Bacteria are single-celled organisms, which means they are made up of just one cell. They can live on their own, eat food, and grow by themselves because they can do all their own life processes.
On the other hand, viruses are not made of cells and are way simpler. They can’t do anything by themselves and need to find a host cell to help them make more viruses. This means they can't eat, grow, or reproduce on their own. Because viruses don’t have the things that living things usually have, like the ability to grow or use energy, most scientists say they aren’t really alive.