Horsey Radish as it's called in Spongebob lol! I've never tried the stuff or maybe I have, I think it's spicy and kinda takes your breath away? My mom loves it. The weirdest thing to me I've noticed on the intetnet is people who love to debate which condiment ia better than the other or what your favourite says about you. I'm like, wtf? Can people just enjoy what they enjoy? A damn condiment.
You've probably had horsey radish in another sauce. It's in most Tartar sauces. You'd know if you get a taste of just horsey radish though. It can be very strong. If you ever get a dozen raw oysters they typically give you a bit with them.