The explanation is complicated. Being raised Lutheran, in Luther’s Small catechism when he explains each commandment he always prefaces his explanation with, “We are to fear and Love God.”
I found one pastors explanation almost adequate, but not quite:
Both fear and love are part of our relationship with God. Fear, in a religious context, means more than emotional terror or dread. It also includes great respect and awe. As a child, I feared my father, but not only because he could punish me. He was bigger, older, wiser, faster, and so many other things than I was. Yet this fear did not exclude love, rather they went hand-in-hand with each other. When I did wrong, the terror of punishment was foremost. However, I also knew that Dad would use his strength, wisdom, and other abilities to protect and defend me, to put food on our table, and to keep scary things away. Thus, I deeply loved him.
I believe I have read other theologians who said that the word “fear” as translated is not adequate to convey the meaning. It is an awe and a trembling, sort of like seeing a tsunami coming towards you, when you realize how insignificant you are in the face of immense power.