What is hydrogenation?what is its industrial application?

Hydrogenation is the chemical reaction between hydrogen and other compounds in the presence of catalyst. . Hydrogenation is an addition reaction.
Example: When ethene is heated with $H_2$ and the catalyst nickel it is reduced to ethane.
$C{H}_2=C{H}_2⟶C{H}_{3}C{H}_3$
Industrial application: Hydrogenation is used in many industrial applications.
For example; in Petrochemical Industry, hydrogenation is used to convert alkenes into alkanes (paraffins) and cycloalkanes. Hydrogenation is also used to prepare vegetable ghee from vegetable oils.