Some Basics In My Humble Opinion

SSC - this is an acronym for Safe, Sane, Consensual and is followed to the letter in any and all alternative lifestyles whereas a negotiation of some sort happens. It is a very important concept for those who enjoy a non-traditional interraction that's emotional, physical, sexual or intellectual with one or more people in a controlled setting to the mutual enjoyment of all parties.  

BDSM - basically an acronym for Bondage, Discipline, Sadism and Masochism

Bondage - voluntary condition of being immobile by use of power, force, influence or object

Discipline - willful training, teaching or development of character or to enhance behaviors

Sadism - obtaining physical or sexual pleasure by inflicting pain on a willful subject

Masochism - obtaining physical or sexual pleasure from pain inflicted from another

Although, webster's dictionary translates these concepts in my opinion, negatively, in terms of the BDSM lifestyle, the community utilizes these ideals as a type of power exchange to enhance the shared experiences between parties, in a willful, protective setting to bring about pleasure and/or pain, or to elicit specific behaviors, outcomes, servitude, and/or to increase mental, sexual, intellectual stimulation.

Play - is the activity that is motivated by role-playing, pleasure or pain and is shared or exchanged between two or more people in a public or private setting. The interraction is often referred to as a Scene - a controlled period that has a designated start and finish time.

What is Impact Play - activity that fosters the highest or most effective result in a BDSM scene. This is obtained through higher administrations of physical pain most often associated with heavier tools, instruments, objects, hands, feet, etc. (often referred to as Toys, i.e. Floggers, Paddles, Whips, Chains, Cuffs, Rope, Masks, Gloves) to increase another's tolerance rather physical, mental or sexual.

What is a Top and/or Bottom - a bottom is the person who wants, desires, or needs to receive physical sensation from a top, the person who is performing or doing, or distributing the actions. Top/Bottom should not be confused with Dominant/Submissive. The biggest difference between the two concepts is that tops and bottoms interract during a specific timeframe that is negotiated beforehand, whereas the other is driven or motivated by a more 24/7 existence in their power exchange (a symbiotic give and take whereas one cannot happen without the other). A switch - is a person who enjoys receiving and giving sensation through pleasure, pain, physical, sexual or sensual interractions in a scene.

Difference between Daddy and Sir - I look at Daddy as a tender SIR.  In my experience, Daddy is a term of endearment whereas the person who looks after you, protects, guides, disciplines, etc., plus the added level of emotional, loving, sexual and romantic relationship wants to be addressed as Daddy.  Sir, is basically the same as a TOP, however, TOP is geared more towards a role played within a scene, for a short time frame, whereas Sir, is a more formal term that denotes a level of respect, admiration, guidance, mentoring, but in most cases the closer more intimate, romantic relationship is not as deep as the Daddy role, although some might disagree, and it's just about how one wishes to be addressed, SIR being more formal. 

Boy, or Boi, Girl - these terms coincide with indentity of oneself. It is not solely representative of biology, but more of how one sees him or herself within the BDSM community.  For example, although I was born biologically female, my characteristics, mentality, interraction to others tends to lean towards a masculine persona.  This is different from trying to pass as male in a society that is hung up on appearances that traditionally fall within standards set forth by how others see you physically or biologically.

What is subspace/topspace? hard to put into words. I think of it as a moment during a scene where the one who is on the receiving end feels a kind of "high" or euphoric similar to when you drink alcohol or if you are a person who works out, that same feeling you get after completing your regiment. This euphoria can happen to the one who is administering the pain as well, although, I can tell you I've been both top or bottom and the feelings are received differently. Subspace can also produce an emotional sometimes spiritual connection to the person who took you there. Often times, it's difficult to talk or communicate because you feel kind of "floaty." By this time, your body has produced the highest amount of endorphins. Often, you come out of this space, feeling exhausted, tired, and in an extremely relaxed state of existence.  For me, it was a very quick way to distress, or a release.  I've cried, laughed, and other times felt like I could rule the world. I can honestly say, when I top, I feel similar because ' I ' took someone there.