Here’s all you need to know to understand the global phenomenon. — A tweet sells for $2.9 million. A digital collage is auctioned for $69 million. Visa Mastercard shells out $150,000 on a jpeg “CryptoPunk” avatar. NFTs, short for Non-Fungible Tokens, repeatedly made the headlines this past year. And the market is blowing up again, with the largest marketplace for NFTs processing…