Well, for starters, only males have a prostate gland, so comparing prostate orgasms to clitoral/vaginal/g-spot orgasms isn’t something that I think most people would be able to do…
As with anything, I expect this will differ from guy to guy. For me, it’s an incredibly intense feeling of release (moreso than orgasms only involving penis stimulation). I can feel the sensation building inside me and around my anus, coupled with stimulation from my penis, until I reach orgasm and ejaculation (which are coupled for me and most, but not all men)
I would second that with the idea that its very intense and it builds up around the whole area. There can be lots of cum, plenty of precum from my experience.
A reddit user sums it up with his experience a little bit here
In my bit of experience with my Aneros, it is indeed very much different from a penile orgasm. Prostate orgasms incorporate a much more internal feeling (as one might expect), but are further distanced by a disconnect from the normal penis sensations male sexuality has been traditionally defined by. This isn’t to say the two can’t be coupled with each other, but its important to note that the prostate orgasm has a much different feeling on its own.
I liked xtheory79’s description of the internalization feeling: “Think of it like this: it’s the difference between feeling warm from the sun on your skin than feeling warm from the inside after taking a shot of really hard liquor”
An analogy for the orgasm might be: that shivering feeling when cold (instead though its quite a warm feeling throughout the body) + tensing and convulsions of the lower back and thighs + limpness of upper body + tingling of the prostate area. Its very much full body, with a lot of emphasis on the back, thighs and buttocks with the center of focus being the prostate inside the pelvis. I’ve found it can last anywhere between 30 seconds to 1 or 2 minutes, with the intensity varying throughout.
Important to note with all this is that achieving a prostate orgasm is a process that can take some time to realize, requiring exploring and consciousness of one’s prostate area. My first time reaching an orgasm came after about 1 month of experimenting and trial. Its best to approach working towards a prostate orgasm as a process of understanding one’s body and learning how to best stimulate the prostate to achieve the most sexual pleasure.
Have as much fun as you want with it. And remember its not just for gay people, there can be plenty of fun anal play for both guys and girls in straight play.