What does it mean when someone says you are the cat's meow?

I'm curious, could you clarify for me what exactly is meant when someone describes someone else as "the cat's meow"? Is it a phrase that's widely recognized or is it more niche? Is it meant as a compliment or could it potentially be used in a sarcastic way? I'd appreciate it if you could provide some context and examples of how it might be used in conversation.