This is google's definition:
a person's sense of self-esteem or self-importance.
"a boost to my ego"
the part of the mind that mediates between the conscious and the unconscious and is responsible for reality testing and a sense of personal identity.
(in metaphysics) a conscious thinking subject.
My definition is pretty close to the one highlighted in the definition.
As the ego (a.k.a. outer-self) is the aspect of your whole personality that interfaces with the physical reality (created by your subconscious), the inner-self is the aspect that interfaces with the non-physical reality (using inner-sense). They aren't two selves; they are two aspects of the same one self (maybe that's what non-dualism refers to (?))
Everything expressed here is what I believe. Keep that in mind when you read my post, as I kept it in mind when I wrote it. I don't parrot others. Most of my spiritual beliefs come from direct channeling guidance. I have no interest in arguing whose belief is right, and whose is wrong. I'm here just to express my opinions, and read about others'.