Nonce is an abbreviation for number only used once. It’s a number added to a hashed (encrypted) block in a blockchain. When the block is then rehashed, it meets the blockchain’s difficulty level restrictions.
The nonce is the number that blockchain miners are solving for. To successfully verify a block, a miner needs to be the first to guess the block’s nonce.
If the miner’s hash meets the requirements set, then the block is added to the blockchain. Searching for a solution in order to guess the nonce is referred to as proof of work. The miner who is able to find the value fastest gets the block reward.