Albumen is egg white or its protein, if you’re into that sort of thing. That’s also what it is even if you’re not into that sort of thing, but, in that case, you probably don’t care.
In theory, according to some people, possibly even including medical scientists, although I’m not sure about that, egg whites are more healthful than the whole egg. That may or may not be so, but here’s the truth: Whether you eat eggs with yolks or just egg whites you’re not going to live forever. Sorry to be the one to break that to you.
Enjoy your eggs.