Final answer:
In chemistry, a substance that loses electrons, making it possible for another substance to gain electrons, is called a reducing agent. The reducing agent is oxidized in the reaction, while the substance that gains electrons is the oxidizing agent.
Step-by-step explanation:
In chemistry, a substance that loses electrons, making it possible for another substance to gain electrons, is called a reducing agent. In an oxidation-reduction (redox) reaction, the reducing agent is the substance that is oxidized and loses electrons. The substance that gains electrons and is reduced is called the oxidizing agent.