Sometimes God showed his presence in visible ways. These appearances are called theophanies (visible signs that God is present). The pillar of fire and the pillar of cloud were examples of this.
These signs assured the people that God was with them and that he was powerful. When the pillar moved ahead, the people followed. They trusted that God would lead them safely to their destination (Exodus 13:21–22; 14:24; Psalm 18:9–10).