Question

what is mean by tautomerism in detail????

Answer 1

Tautomers are isomers of a compound which differ only in the position of the protons and electrons. The carbon skeleton of the compound is unchanged. A reaction which involves simple proton transfer in an intramolecular fashion is called a tautomerism.
Keto-enol tautomerism is a very common process, and is acid or base catalysed. Typically the 'keto' form of the compound is more stable, but in some instances the 'enol' form can be the more stable.

Answer 2

Tautomerism :

The isomerism in which a single compound posses two structures which are in equilibrium with each other by shifting of a proton.