Tautomers Definition:

Constitutional isomers that rapidly interconvert via the migration of a proton.

Tautomers Explained:

In a chemical equilibrium between a keto form (a ketone or an aldehyde) and an enol which is alcohol. The keto form predominates at equilibrium for most ketones. The reaction which includes simple proton transfer in an intramolecular manner is called a tautomerism.