Each font will contain its own set of symbols, so I’m guessing you’re looking for definitions of Apple system fonts. There’s a good “Overview” here:
https://developer.apple.com/design/human-interface-guidelines/sf-symbols/overview/
If you are searching for a particular symbol, it’s best to use the Keyboard Viewer, and there were two excellent articles in TidBITS a few years ago:
And this article about character and keyboard viewer:
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