The Hebrew word for "glory" is from the same root word for "heavy/weighty". Glory refers to the sheer, mind-blowing, weightiness of God's presence. (And this metaphor fits with the extreme reactions of people in the Bible who get even a glimpse of God's glory. They are literally/physically blown-away, overcome, almost crushed at times as they glimpse the “weightiness of God”). As one might describe a King’s glory so the Bible tells us that God’s glory is so awesome that even the angels in heaven bow down on the ground before Him (see Revelation 19:1-2, 4).
The Bible teaches us that God is one God (Deuteronomy 6:4) and there are no other Gods beside Him (Deuteronomy 4:35, Isaiah 45:5-6).
However, in Genesis 1:26 God says Let us make man in our image, in our likeness, and the plural words "us" and "our" which are used here, are Hebrew plural words which means "more than two". As we read through the Bible we are introduced to God the Father, God the Son, and God the Holy Spirit, all of whom are one God (Deuteronomy 6:4).