I assume you have two eyes, right? What happens when you close one eye and only have monocular vision?

Not much, but it's a lot harder to judge distances correctly. You still can, if you use outside knowledge and perspective, but it's less accurate.

Same for stereo hearing. With two ears it's easier to locate where a sound is coming from. With one ear you can tell if something at constant volume is moving away or moving towards you based on loudness. With two ears you can tell if something at constant volume is stationary or circling around you.

Unfortunately I don't think there are words to describe it. You "just know", because it's an unconscious brain thing.

You could sort of simulate it by rotating your head 180 degrees and noticing how the sound changes. People with two working ears can do this without moving their head.

The effect for music is mostly: it's easier to separate instruments even if they are the same volume, if they are in different spatial locations so the brain can filter against it. Stuff can sound less "cluttered, muddy", but it doesn't help as much as you think in recordings because you as a listener can't move the microphone. I think it would be a bigger deal in small live shows, or music performed in virtual reality where a 3D engine can calculate the audio delay appropriately for each ear, and that difference is relevant because you the listener are close to the musician and possibly moving relative to them.

There’s been some wonderful recordings that were designed solely/primarily for mono playback (early Motown/rock n roll/blues for example) that IMHO actually kind of benefit somehow from lack of stereo separation. If mixed well, the instruments can blend really well and work as one unit and there’s kind of an energy and punch to the speaker/s working as one... Early stereo records often had rather drastic left/right panning (eg. some Beatles stuff) or had to hedge their bets in case they were played back through eg. mono radios/badly set-up stereos and so on… Something similar is still the case when engineers think about what their track might sound like coming through a crappy mono phone speaker with no bass at 128kbps/what have you… The advice I’ve always heard is that you should make sure that your mix would ‘fold down’, so to speak, to mono anyhow… So you should never rely on the listener being in the sweet spot (if you think about eg. a club where an audience member could be stood directly in front of one speaker, but barely hear another, or some listeners weird home setups with one speaker balanced on a bookcase and the other on a table or something). In most environments you get complicated reflections and build ups/absorptions of various frequencies due to the acoustics anyhow… Although with single-sided deafness you won’t get the effect of directionality from the delay between the sound hitting one ear before the other, I imagine you would still experience the attenuation of certain frequencies as the sound moves around your head, the height dependent effects and so on …I suppose it’s not a million miles away from if you were to close one eye - monoscopic as opposed to stereoscopic? Bass frequencies are mostly experienced more or less monophonically, so you’re not missing out there... I wonder if reverb effects/using impulse responses of different environments and volume adjustments might also help give some of the impression?

What the other comments said, but keep in mind that it's not very precise in normal circumstances: you have an extremely rough estimate of direction (along all axis) and distance.

You can increase the accuracy if you are afforded the opportunity to concentrate on the sound.