Roles and Titles
The BDSM community has many 'titles' or roles. In some cases, these roles or titles are self assigned, and therefore become a preference. In other cases they are assigned based upon the dynamics of how a relationship forms, or the role they naturally assume in said relationship.
Generally, roles and titles are non-transferable. This means that, if someone has granted someone else the title of their "Master", this doesn't mean that outside of that relationship they should claim that they are a "Master" in relation to others whom may not have formed a relationship with them yet. That being said, someone could state that they have been known as, or given the title of Master in past relationships. But claiming to be a Master in general is seen in poor taste. We are all always learning, and each relationship dynamic is new and should require a fresh start. A Dominant person should be mature enough to realize that they aren't God, and therefore they still are in a position to learn more.
The following are some of the roles and titles commonly encountered.
Alpha:
The Alpha type personality is a personality of power and leadership. Typically this is a self assigned title based on someones knowledge of their own personality, and the role they seek. In my opinion, Alpha is the best way for a Dominant type to describe themselves when they are not in a formal relationship.
Dom / Dominant:
A Dom is a term which is given to those who have had a submissive submit themselves to them. Typically and properly the term "Dom" refers to someone who is currently engaged in keeping a submissive under their influence. It is a title and role which should properly be reserved for people actively engaged in a Dom/sub relationship.
However, in many cases "Dom" is used to self title someone based upon their desire to seek to Dominate someone.
The title Dominant in full, is rarely used, but when it is it is typically used in a general sense to describe someones personality. This is what people who claim to be "Dom's" should probably say instead of saying "Dom".
sub / submissive:
The title and role of "sub" is one which is given to those who are in an active D/s relationship. The role and title is implied when the submissive decides to give the gift of submission to their chosen Dom. Someone who is a 'sub' should only be referred to as a sub within the context of the relationship they have submitted within. The reason I suggest this is to try to battle the misconception that just because someone claims to be a 'sub' they become fair game to anyone who wants to 'Dom' them.
Popular culture however goes against this, and often 'sub' is used to self label someone, and thus invites confusion.
The title submissive is a generalized term, which can be used to describe someones personality or relationship preference. Again, just because someone labels themselves as a submissive, doesn't give anyone else the right to try to force their submission.
slave:
In the BDSM community, slaves are typically submissives who have consented to a long term agreement where they become property of their Dom's or Master's. They will typically be collared in some sense, or maybe even marked with a tattoo, or scar. As typical in BDSM culture, a slave may request to be uncollared and freed at any time and their 'owner' must obey.
Master:
The title Master can have a couple meanings:
1. A student learning from a more experienced partner in the BDSM sphere, may call their mentor a Master. Doing so does not change their own title or role.
2. A Dom whom keeps a slave may be referred to as a Master of their slave.
Mistress:
The title Mistress can have a couple meanings:
1. The head female in a female harem (typically made up of submissives) may be referred to as a Mistress.
2. A female Domme or Dominant may be referred to as a Mistress if they have earned the title from a submissive.
3. A female submissive, whom is the primary lover of a Dominant male in a household with more than one female, may be called a Mistress by anyone, typically save for the Dominant male.
Domme:
Domme is typically a term which is self entitled. However, like Dom, it is a term which must be earned within a relationship. It is more often used to describes someone preferred choice, rather than to imply any sort of dominance. Typically the term Mistress is used once a domination is established.
Sensi:
The title Sensi is sometimes used to describe a more experienced person, whom is skilled at teaching and educating those looking to learn about various aspects of the BDSM lifestyle.
switch:
A switch is someone who switches roles within the same relationship. Sometimes they may act as the Dom, others the sub. Everyone is capable of switching roles between relationships, but switching roles within the same relationship can be more of a refined skill.
brat:
A brat is typically a submissive who enjoys engaging the attention of a Dominant by way of intentionally doing things she knows will upset the Dominant, in order to focus his attention on her.
little (lg) / babygirl (bbg):
A little, or babygirl is typically a submissive whom enjoys roleplaying as a younger girl. They tend to crave the love and attention of a "Daddy Dom" (or DD). Typically littles will not seek punishment as much, and when they do, they prefer lighter punishments such as spanking. They generally prefer the non-sexual attention of their dominant partners, and also prefer guidance and some form of support or stability from them.
"Daddy Dom", Gentle Dom:
A Daddy Dom, or a Gentle Dom is a dominant who enjoys nurturing and guiding their submissive. Typically they will be focused on self improvement, motivation and generally companionship. Typically these dominants do not venture too far into a sadistic stance unless inspired to consensually by their partner.