Vivisection is experimentation on a live animal. The word comes from the Latin vivus, which means "alive" and the English section, which means "cut." "Vivisection" is understood to include any type of experimentation on any type of animal, regardless of whether the animal is literally cut. The term includes both scientific experiments and product testing. Those who conduct the experiments are known as "vivisectors."
Animal welfare advocates focus on improving the treatment of the animals in laboratories, or oppose only certain types of animal experimentation. For example, animal welfare activists might demand larger cages or anesthesia during invasive procedures, and might oppose cosmetics testing but not scientific experiments. Animal rights activists categorically oppose vivisection because it infringes on the animals' right to live and be free.
Learn more about vivisection, including the laws protecting animals in labs and medical advances made without vivisection, here.