$H_2O_2$, or hydrogen peroxide, is a chemical compound consisting of two hydrogen atoms and two oxygen atoms. It is a colorless liquid that is widely used in various applications, including as a disinfectant, bleaching agent, and in the production of other chemicals. In the context of the topics 6.11 A Comparison Between Biological Reactions and Laboratory Reactions, $H_2O_2$ is an important compound to understand, as it plays a role in both biological and laboratory reactions.