What does the non-dictatorship principle of the Arrow theorem mean exactly?

According to Wiki:

The property of non-dictatorship is satisfied if there is no single voter i with the individual preference order P, such that P is the societal ("winning") preference order, unless all voters have the same P. Thus, as long as there are voters in the society that have different preference orderings, the preferences of individual i should not always prevail.

What exactly does that mean in practice? What would be an example of a "dictator" in a real world election?