I have allways liked to think of it like this:

We are all born with different qualities that in some cases and situations etc make us more or less submissive or dominant than in others.

For example mothers and fathers are often dominant over thier children.

The police officer who pulls me over for speeding is holding at least temporary dominance over me (or any one else that gets pulled over lol).

When teaching class at school I am dominant over my students.

When kneeling before my Owner He is dominant over me.