Pizza Sats are the satoshis resulting from the first commercial transaction: 10,000 bitcoins used to buy two pizzas in 2010.
There are therefore 1 trillion satoshis resulting from this transaction, i.e. 1,000 billion. An impressive number. Of these satoshis, 100,000 have a palindrome identifier. And only 3,000 of these palindrome pizza satoshis were mined in 2009.
The pizza transaction has become part of Bitcoin culture, and is celebrated every year by the community on Pizza Bitcoin Day, May 22, 2010, the anniversary of the transaction.
Palindromes are exotic satoshis, and those from this transaction are actively sought after; and those from 2009 are extremely rare. To date, only 285 pizza palindrome satoshis from 2009 have been found.