A reducing agent is a substance that donates electrons to another substance during a chemical reaction, causing the other substance to be reduced. In this process, the reducing agent itself gets oxidized. Common examples of reducing agents include metals like zinc and sodium, as well as compounds like hydrogen gas. Reducing agents play a crucial role in various chemical reactions, including redox reactions, where oxidation and reduction occur simultaneously. They are widely used in industries, such as in the production of metals from their ores and in organic chemistry for synthesizing different compounds.