Alice triggered a Bitcoin transaction to Bob. The transaction is now in the mempool with thousands of other transactions from other market participants. This is where the Miners come in. In our example the miners are Bob, Carol, Dave and Eve. Each of them picks a transaction from the Mempool and writes it down on a digital notepad. In doing so, they check that the transactions are valid.

The Hash Rate

After Bob, Carol, Dave and Eve have checked their note sheet with the open transactions, each of them starts to solve a complicated algorithm. The crucial point here is that she can only solve the puzzle (the algorithm) by continuous guessing. You only have an advantage if you can guess faster. This guessing costs energy. The higher the computing power (hash rate), the faster you can guess.

History of Bitcoin Hashrate (2 years) Source:

The hashrate in the Bitcoin network

The hashrate per second (also H/s) indicates how many times per second the computers try to guess the solution of the proof-of-work puzzle.