Answer:
When atoms bond together to form compounds, they attain lower energies. The difference between energies of the bonded atoms and individual atoms is released in this case.
Similarly, when the compounds, like water, are broken, energy is absorbed, and the resultant atoms have higher energy.
2H₂O ⇒ 2H₂ + O₂
The energy required to break this bond is known as bond energy.
For example in the given reaction, 469kJ/mol is the bond energy absorbed to carry out the reaction.