In the context of cryptocurrencies, mining is the process of hashing a nonce until the required number of leading zero bits in front of the block’s hash is found. To see if the proof of work is valid, the Bitcoin timestamp network checks for those leading zeros. The difficulty to find a valid hash is adjusted over time so the blocks are always roughly created at the same time (around 10 minutes for one Bitcoin block. The usage of the word comes from mining for physical gold.