Code PO420 something about my CAT-Conv

I have a 2000 Maxima with 56k miles. My CEL is on and Autozone pulled code PO420, something about the Catalytic Converter. Any experience
with this code?

My car runs fine, gas milage is ok and sounds good. Any feedback what the problem may be?

have your dealer check it , my max did the same w/38k and it turned out the cat wears down over time, but the computer cant realize this, so it freaks out , all they do is reprogram your ecu, if thats not it , its emmisions related , more than likely