The meme is literally correct. when you make an audio file into an mp3, it takes some of the sonic information that our brains are bad at noticing and just...completely removes it(to save storage space). if it's a high quallity mp3 its essentially completely unnoticable. That's why it's psychoacoustic, it uses psychology to fool your brain into thinking it sounds better than it does, litterally.

Psycoachoustic is basically just a big word for taking into account how our brains deal with what we hear.

Also I'm not saying mp3 is bad, in fact I think the opposite is true. I think it's good to think of it like being the .JPG of audio, you're not getting the original quallity and that's the point and unless you need to do manipulate that audio file and its a reasonable quallity then you likely won't notice the difference.

Ogg vorbis (.ogg) is a better codec though IMO.

*edited for spelling and grammers