btw it also doesnt necessarily say anything bad about you. bdsm is fairly common, so much so that I don't really consider it abnormal or something people should freak out so much about. No one i know publicly admits to liking it, yet dating ads and secret clubs for it are incredibly prolific in mid ohio
Ariasderros covered some of it already.
BDSM is not one thing, not two things, but
three things.
B/D is bondage and discipline.
Two quick nitpicks, discipline does not always mean punishment despite it's common usage as an euphuism for such and technically speaking bondage denotes slave and it's synonyms include servitude, thrall and serfdom so it's not simply handcuffs.
But often it is focused on binding someone and punishing them. The key element is that it is punishment, not unwarranted pain and humiliation. For instance if your GF wanted to lose weight and you told her run five miles on the treadmill every day and she didn't, then you would follow up with something displeasing. Hopefully with a clever trick like trying her to the treadmill
D/S is dominance and submission.
This doesn't always include handcuffs. Ever told your mate to lay still as you tickled them? How about ordering them to get on the treadmill? D/S is the most wide ranging, if a women is sitting on your face telling you to lick harder you're the bottom, and I'm not meaning your position on the bed.
S/M is sadism and masochism.
And you know what? It's not a well kept secret that most guys you know are not into getting their balls kick, most guys simply say fuck no to that. Jesus-isn't-fucking-Pelor who with a functioning nervous system would want that? It could very well mean a light spanking you know or the much more popular nipple biting. It's the women's nitrous button right? *wink*
As you can see, even in each part of the large acronym there is plenty of variances of sexual and even nonsexual acts to be had. Like peeing in someone's face could be S&M ( they enjoy it because they don't), D&S (fulfillment of following orders), B&D (demonstrated helplessness to resist), or grounds for them to throw up on you (it's piss). Maybe all of them apply, maybe some don't. Like your GF giving you a BJ because it pleases you and not for the great tasting reward.
Maybe they don't admit to it because they didn't check the box next to "all of the above" eh? Like for all my rope talk and spiffy BDSM avatar, mostly I just break out the ropes and tease when I'm feeling playful. I'm not really into the S&M side at all.