If you want to make tender and melt in your mouth eggs then you should salt the eggs before cooking them.
If you just want salted eggs then you can salt them either before cooking them or you can wait and salt them after cooking them.
Salting the eggs before cooking the eggs makes the eggs tender and they melt in your mouth much better than just regular eggs without added salt.
When you add the salt to the eggs before cooking the eggs the salt then dissolves the eggs proteins and allows them to create a moisture-binding network.
That is what helps to make the eggs moist and easier to chew and melt in your mouth.
For the best eggs such as the best scrambled eggs you should add salt to the eggs before cooking them.