In chemistry and physics, the exchange interaction is a quantum mechanical effect that only occurs between identical particles. Exchange energy is the energy released when two or more electrons with the same spin-exchange their positions in the degenerate orbitals of a subshell.
We can define it as:
The energy released when the anti-parallel electrons belonging to a degenerate (same energy) subshell are made to have parallel spins.
Exchange energy forms an important part of the covalent bond of many solids and is also responsible for ferromagnetic coupling.
That’s a pretty clear description. Thanks a lot!