In a world in which people worshiped many gods, God reveal which one he is in three simple Hebrew words, ehyeh asher ehyeh. We translate it, I am who I am. The problem is that our thought patterns are still, whether we know it or not, rooted in Greek philosophy. We hear "I am" and we think existence, being, "To be or not to be", or "I think therefore I am.". But this is not the Greek of the New Testament. It is Hebrew, Semitic not western thinking.
The purpose of the word used here is not to say "I exist." In this acclamation, God proclaims his powerful active presence. He is proclaiming himself to be the God who was with Abrahsm, with Issac and with Jacob. He is not a far off God; he is present. He does not passively watch; he will be constantly at work in their midst.
God tell the people of Israel that he will save them, but he does not reveal how. They must trust him with that.
For us as Christians the ultimate salvation/liberation will be carried out through another good shepherd, Jesus Christ. God will also reveal that the constant active presence since the dawn of creation was, is and always will be the third person of a trinity, the Holy Spirit.
The same God who revealed a bit of himself through a burning bush to Moses, at a later time revealed himself fully in Jesus.
The same God who has been constantly present and active over all these years, is still present and active today. Do we have the eyes of faith to see it? Do we recognize his presence with us? Do we acknowledge and thank him for his action?
Three simple words spoken to Moses remain the foundation of our faith. May we have the grace to believe.