The Self. The Observer. Each of these plays a significant role in our experience of reality.
The Self is; the observer knows.
Did you ever do something and wonder "Why did I do that?"
The Self did it; the Observer noticed and wondered about it.
Your Self is You, it is the "I" you refer to when you say "I am hungry"
"I am happy" "I am sad."
And yet, you are also the Observer that can step outside of Self and consider what Self is doing and being at any given moment.
Seek to understand who Your Self is, why they are the way they are, what they are doing, where they are going in this life, and why.
Know Your Self. After all, no one can know you like you can know you, but you can only really know your Self if you try.