Bitcoin Hashrate and Difficulty.
This chart shows the Bitcoin network hashrate, hashrate 28 day moving average, and difficulty of the Bitcoin network. The hashrate is an estimation of the number of hashes the network is computing at any given time. The exact hashrate is actually unknown, and is estimated from the average time it takes to mine a block and the current difficulty of the network. As the hashrate increases, it becomes more likely that a block will be mined in less than 10 minutes, thus causing the average block-time to decrease below that target. This causes the difficulty level of the network to increase thus ensuring blocks only take approximately 10 minutes to mine. If the hashrate decreases, then the reverse happens.