Is referring to a relationship where there is a clear distinction of power between the dominant party (master) and submissive party (servant).
In this relationship where one (the master) has complete authority over the other (the servant) in directing the manner, place, and time of his or her services. This is in contrast to employer-employee relationships because an employee has all the least some discretion in performing his or her duties, and to principal-agent relationships because an agent usually has broad discretion in conducting his or her business.
In BDSM, Master/slave or M/s is a relationship in which one individual serves another in an authority-exchange structured relationship. Unlike Dominant/submissive structures found in BDSM in which love is often the core value, service and obedience are often the core values in Master/slave structures. The participants may be of any gender or sexual orientation. The relationship uses the term "slave" because of the association of the term with ownership rights of a master to their slave's body, as property or chattel. While male "masters" will usually be referred to as "Master," whether or not female Masters are referred to as "Master" or "Mistress" may depend upon whether they identify as following the "Leather" or BDSM path.
Outside the BDSM community, the relationship of Master/slave is sometimes regarded as a form of consensual sexual slavery. In BDSM, a slave is a specific type of submissive. The Master/slave relationship refers to the relationship between the individuals involved, and does not necessarily require any specific acts, sexual or otherwise, though sexual activity is usually an aspect of the relationship. The sexual aspect could be conventional, and not necessarily BDSM. A slave could also be a masochist or bottom, but this is not always the case.