What is Bitcoin's hashrate?
How many guesses a second all of Bitcoin's miners make together. More hashrate makes the network harder to attack.
Each guess is a hash: a fingerprint of a possible block. The network's total is measured in exahashes a second (EH/s), each a billion billion guesses, and above a thousand of those in zettahashes a second (ZH/s).
Whatever the hashrate, Bitcoin adjusts its difficulty so that blocks keep arriving about every 10 minutes.