Spanking can form a part of sexual play.  A spanking is usually administered by a Dominant to their submissive/slave and can be done with an open hand or an object such as a paddle or hairbrush, to heighten sexual arousal for one or both parties. Spanking is usually enjoyed by those who find sexual pleasure in receiving pain (masochists). 

Spanking is done in a variety of positions. A 'spanking bench' is a specific piece of furniture designed for someone to lean/kneel over whilst they are being spanked.  Another position is 'OTK' (over the knee). 

Dominants may remain clothed whilst their submissive/slave can be in any state of undress that the Dominant prefers or instructs.  Spanking through clothing does not create the same sting or leave cheeks 'blushing' a beautiful shade of rosy red.

Spanking is often used by Dominants in BDSM to exert control over their submissive/slave or to punish them for bad behavior or not following instructions. 

The dominant may remain clothed, while the submissive can be in any state of undress the dominant prefers. The submissive may come to the dominant without underwear or wait for the dominant to remove it. The dominant may also spank the submissive while they are wearing underwear, although this does not create the same sting.

Spanking is also referred to as erotic spanking or 'spankophilia'.