What is a Sub Top like?

I honestly have a bit of trouble thinking what a sub top would be like. I know that a top doesnt necessarily have to be dominant, but I guess I just want to know how a sub top feels. Im not one, but its good to know how other people experience something before casting judgement. So, what do you think?

My understanding is that the sub does the topping as an act of service to the person being topped--presumably their dominant, for example. I suppose a scenario could also exist where the sub's dominant ordered them to top another person such as another sub or another person. The sub does this topping activity (whatever it is) from a subordinate position and under the direction of their dominant--not as an act of dominance in itself if that makes sense. The act of service model or similarly the obedience model are the two scenarios that make the most sense to me in terms of the situations in which this might take place. I hope that helps.