The reaction is given below

${\mathrm{BaCl}}_{2( \mathrm{s})} +2{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{l}\right)}⟶ {\mathrm{BaCl}}_2.2{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{s}\right)};\mathrm{\Delta H}=-\mathrm{x} \mathrm{kJ}.$

The value of $\Delta \mathrm{H}$ represents

${\mathrm{BaCl}}_{2( \mathrm{s})} +2{\mathrm{H}}_2{\mathrm{O}}_{\left(l\right)}⟶{\mathrm{BaCl}}_2.2{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{s}\right)};\Delta \mathrm{H}=-x \mathrm{kJ}.$

The energy released is called the enthalpy of hydration. In simple terms, enthalpy of hydration is described as the amount of energy released on dilution of one mole of gaseous ions. It can be considered as an enthalpy of solvation with the solvent being water. Hydration enthalpy is also called hydration energy and its values are always negative.