The meaning of "How are you?" is a:

• Greeting: It's a polite way to initiate a conversation.
• Inquiry about well-being: It's a question that invites the other person to share how they are feeling, though often a short, positive response is expected.

Essentially, it is a standard social nicety, similar to "Hello," and doesn't always require a detailed answer.

More information can be found at: Cambridge Dictionary