When internal and external stresses are equal, the material will not undergo any net deformation. In other words, the material experiences an equilibrium state where the applied external stress is balanced by the internal stress within the material. This condition is known as the elastic limit or elastic deformation.

In the elastic region, materials deform under applied stress but return to their original shape when the stress is removed. The internal stresses within the material result from the stretching or compression of atomic or molecular bonds. These internal stresses counteract the external stress, preventing any permanent deformation.