Ok, it is a fair question, when one is new to the ways of D/s, M/s, etc.
Some of us are referred to as whores and sluts...frankly, I have been both. I am now a former slave who is now a submissive, due to life's circumstances. I am a bit offended that people who are slammed for our sexual kinks will be so judgemental of anyone else.
I was a slut, as I have already stated, and enjoyed being "easy". The thrill of getting paid to "play" was an exciting endeavour for me. I am not ashamed, as this was a form of experimentation, and part of my journey into the wonderful world of BDSM.
Before I discovered BDSM, I was a sex slave...since I didn't understand that the sexual appetite I had was not only about sex. I was a slave to my own misguided sexuality, and constantly felt like something was wrong with me..."sicko"...which is what much of the vanilla world deems us all.
Having said that, I do also agree that the differences are pretty clear. I am His whore, His little slut...but am no longer just a whore. I was missing out on the benefit that a slave or submissive enjoys, if they are blessed to have someone to use them, abuse them, and take care of them like the precious being that they are. Whores and sluts don't get to feel cherished...only used, which is also not a bad thing, if that's what turns them on.