Communication affects a relationship in many ways. Firstly, it allows the participants to grow closer to one another through sharing their thoughts and feelings. For many people having a close mental and emotional bond with their partner is an important part of their relationship. Without effective communication, that bond can not be created. 
  

Secondly, it allows each person to learn more about the other person. In a d/s relationship that is very important for both a dominant or a submissive. A submissive can't meet the needs of the dominant unless he/she knows what those needs are, and what makes the dominant happiest. A dominant can not make informed choices for the submissive's best interests, if the dominant does not know the submissive's desires and likes or dislikes.  

Communication breeds trust in the relationship. The better you get to know someone, the more you either trust or distrust them. Without communication, trust can not grow and a d/s relationship relies on trust to be satisfying.  

Many are confused as to what is true communication and what is not. Barking out orders and expecting total obedience in return, is a form of communication, but it is not the communication that builds the relationship. When we talk about communication in a d/s relationship, we are discussing the ability of the participants to talk to one another. Conversations about mundane things, emotions, problems, concerns, and anything else, is communication. In a relationship, the ability to talk to one another is of utmost importance to keeping the relationship alive.  

How does one communicate effectively in a d/s relationship? This differs for everyone, but some of the basics of effective communication apply to every relationship. First you have to be able to talk. To place your thoughts or feelings into words, then express those words to your partner. Second, and the hardest part of communication, you have to know how to listen. By that I mean, really listen. Not pretend to listen, or hear only bits and pieces, then finish the sentence for the speaker. You have to be able to calmly listen to what your partner is saying, and actually hear it.  

Don't form your rebuttal or answer BEFORE he/she has finished speaking. Wait until they are done speaking, then think for a moment before answering. Don't interrupt when the other is speaking. This shows that you care about what your partner is saying and you are truly interested in hearing what they have to say. By doing this, you make your partner want to talk to you more because they will feel heard. This is especially important with a woman. Women prefer to talk things out, so listening when a woman is talking can make you look "great!" in her eyes.  

Being able to actively listen, can prevent quite a few problems caused by misunderstandings. Do not be afraid to ask for clarification if the speaker says something you don't quite understand. It is safer to ask for clarification than to just assume what you think the person said.  

Good communication skills take practice to develop. Specially since everyone communicates differently. In a relationship it becomes a matter of adjusting to the way your partner talks and being able to adjust your communication skills to match. When it comes to communication problems, the best solution is meeting each other half way. For example, if one person normally keeps their feelings, thoughts and fears to themselves, and the other prefers to talk things out, it is a good idea to meet each other half way. The one who prefers to be quiet, can make more of an effort to open up more often. And the one who prefers to talk all the time, can learn to differentiate between babbling and really talking, and hence learn to not talk so much. In this way, effective communication can be reached.  

As you can see communication is indeed important and without it, the relationship will not survive. I once read the book "Men Are From Mars, Women Are From Venus". I found it to have a wealth of information on the communication differences in men and women. From reading this I was able to understand why men prefer to withdraw and why women would get upset when someone tried to solve their problems. I recommend reading the book. All of it may not apply to you, but guaranteed you will find at least one thing that does apply to you or your partner. It can create a deeper understanding of your partner and open up whole new ways of communicating with each other.