Bitcoin blockchain rookie question how is nonce the secret number added to each block generated

Question

My understanding is that bitcoin minors are all essentially searching for a secret number, which is added to each block of transactions to make the guessing work more difficult. Once plugged into a hash function, the block and the secret number together generate the correct hash, and whoever finds the correct hash gets rewarded.

My question is: Where does this secret number come from? Who gets to decide it?

Answer 1

It isn't a secret number but it's a 256-bit SHA256 output represented as a 64 char hash digest, in other words, it's any 64 char hash value that starts with the specified quantity of zeros, for example, if the bitcoin algorithm specifies that it must start with eight zeros then a sha256 hash digest of 00000000a16506ee98e8de04e91638d614546a116580c7d81d5807616cba8096 will mine the block, any hash digest that starts with eight or more zeros will mine the block. There are multiple correct answers, first, to guess the correct answer mines the block, gets the reward.