heimanman

Hi all, I am not familiar with cars, other than checking engine oil, fluids, filling the gas tank, and driving. My 98 Corolla engine light came on and it was diagnosed with the Code P0420. On the machine, its description is Catalyst Efficiency Below Threshold (Bank 1). I went to AutoZone see if they know what it is, they have no idea. My cousin told me that it tells me I have to change the Catalystic Converter. How can I ever find out ? Can anyone help me please? Thank you.