Keto-enol tautomerism is a chemical equilibrium between two forms of a compound: the keto form, which contains a carbonyl group (C=O), and the enol form, which has a hydroxyl group (–OH) attached to a carbon-carbon double bond (C=C). This process involves the transfer of a hydrogen atom and a shift in the position of the double bond, allowing the compound to exist in both forms. The keto form is generally more stable than the enol form due to stronger C=O bonds. However, the enol form can be significant in certain reactions, such as aldol condensation and Michael addition, where its reactivity plays a crucial role in organic synthesis.