If you know anything about music theory or play an instrument yourself then you may be aware of 440hz being a tuning standard for a note of A from which all other notes are derived (hence it is referred to as A440). However, it’s possible to use different pitches as the base note, and some interesting scales and melodies can result from this. However, separate from the aesthetic qualities of different pitches and scales when compared to one another, there exists a subculture and ideology that treats the definition of this note with a smattering of pseudoscience mixed in with a small helping of belief.
Enter 432 Hz. Many people believe that music written in this key, with A being pitched down a few Hz, is closer to the “natural resonant frequency of the universe”. Some people also believe that humans operate on this frequency, referring to things like DNA, cells and energy, and they claim that the music can have healing properties when in this key. A more normal reason for the popularity of A432 is that it happens to be an easily workable number (it can be referred to as “composite” - the opposite of “prime”) and so it is easy to derive the other notes as a result.
People talk about things like “cosmic energy” - using the standard pseudoscience trick of using proper words in incorrect contexts and forms. Music at 432 Hz is claimed to elicit more positive feelings in the listener, whereas A440 is claimed to be more aggressive. There is, of course, no evidence at all to confirm any of these beliefs, nor is there any to confirm the claim that A440 was developed by the Nazis to brainwash people. Clearly the only reason for different tunings is for aesthetics of the sound, and how that works with different instruments and emotions etc.