A major element of 4'33" is that it is impossible to experience silence. It was partly inspired by Cage's experience in an anechoic chamber. He'd expected to hear silence but could still hear sounds that were coming from himself (the story is that a sound engineer told him the sounds were his bloodstream and his nervous system, but I find it very hard to believe that what he heard was actually either of those things).
4'33" is intended to be "performed" for an audience, and the sounds created by the audience, and any other ambient sounds are the music. Another major aspect of the work is that it blurs the lines between composer, performer and audience. In traditional classical music, the performer interprets the written work by the composer and the audience just listens, but there's no particular reason that all music has to work like that.
It's a shame, but its privacy policy[1] is pretty clearly contravening the GDPR. There's a link on the top of the privacy page which seems to be supposed to show you a consent modal, but it doesn't work on my Chromebook, and their claimed justifications for using the user's data are clearly not actually justified.
4'33" is intended to be "performed" for an audience, and the sounds created by the audience, and any other ambient sounds are the music. Another major aspect of the work is that it blurs the lines between composer, performer and audience. In traditional classical music, the performer interprets the written work by the composer and the audience just listens, but there's no particular reason that all music has to work like that.