Add Lemon Juice While Preparing Eggs

What does this advise mean for peeling eggs?
Before you boil the eggs, slice a lemon in half and brush the halves on top of the shells. You may also add a quarter of a lemon to the water while the eggs are cooking. Next, drop the eggs into the water and let them rest until they reach the consistency you like. As you can see, the membrane will come right off after cooking. The eggshells may now be easily removed.