CNFT means (Cardano NFT) is a digital marketplace created by Cardano Buzz, a popular Cardano staking pool.
It's one of the earliest Cardano projects.
I have used it a couple of times now to sell some of my Cardano NFT's. I just hook up one of my many Nami wallets (usually a wallet that only has the items I want to sell in it) then hit list, input the price and wait for an offer.
If a buyer comes along, they purchase and commit the ADA, I then get a notification and and email. I then directly open CNFT directly from my desktop browser (I DO NOT EVER CLICK ON LINKS THAT COME IN FROM EMAIL) login and send the NFT to the address presented.
I wait 1-2 minutes and the ADA appears in my wallet.