Top, Bottom, Versatile and Dominate, Submissive, Switch explained:

The terms topbottom and versatile are used to describe roles for the duration of a sexual act, or may be used more broadly as a psychological, social, and sexual identity, as well as indicating one’s usual preference.

The terms dominant, submissive and switch are used in BDSM, with slightly different meanings although the terms are also sometimes used interchangeably.

Top: A partner who applies stimulation to another, and who may or may not be dominant, or a dominant partner in BDSM play.

Bottom: A partner who receives stimulation from another, and who may or may not be submissive, or a submissive partner in BDSM play.

Versatile: Someone who participates in sexual activities sometimes as a top and other times as a bottom, also know as switch.

Switch: A switch is someone who participates in BDSM activities sometimes as a dominant and other times as a submissive.

Dominate: Those who take the superior position in dominance and submission scenes and relationships are called dominants, or doms (male) or dommes (female).

Submissive: Those who take the subordinate position are called submissives or subs (male or female).

A top filling the dominant role is not necessarily a dominant, and vice versa, and a bottom is not necessarily submissive.

Now how it’s gets complicated:

Many distinguish top/bottom from dominant/submissive by seeing top/bottom as an expression of physical power, while dominant/submissive is an expression of psychological power.

The main difference between a dominant and a top is that the dominant ostensibly does not follow instructions, although they are limited by what the submissive is willing to do. The top may sometimes even be the partner who is following instructions, i.e., they top when, and in the manner, requested by the bottom. Contrast this with the pure dominant, who might give orders to a submissive, or otherwise employ physical or psychological techniques of control, but might instruct the submissive to perform the act on them.

The main difference between a submissive and a bottom is that the submissive ostensibly does not give instructions, although they do set limits on what the dominant can do. A bottom is not necessarily a submissive; they may enjoy intense physical and psychological stimulation but not submit to the person delivering it. Similarly, a submissive might not be a bottom; they may enjoy taking orders from a dominant without receiving any physical stimulation. For bottoms who are not submissive, the bottom is most often the partner who is giving instructions—the top typically tops when, and in the manner, requested by the bottom.

Related terms:

Topping from the bottom is a related BDSM term, meaning a person simultaneously adopts the role of bottom and dom.

service top is a person who applies sensation or control to a bottom, but does so at the bottom’s explicit instruction.