Hashrate is a measure of the computational power per second used when mining. More simply, it is the speed of mining. It is measured in units of hash/second, meaning how many calculations per second can be performed. Machines with a high hash power are highly efficient and can process a lot of data in a single second. In the case of Bitcoin, the hashrate indicates the number of times hash values are calculated for PoW every second.
Hashrate is usually measured in units of k (kilo, 1,000), M (mega, 1 million), G (giga, 1 billion), or T (tera, 1 trillion). For example, 1 Mhash/s indicates 1 million hash calculations are done every second.
Bitcoin's hashrate increased from 2016 through the fall of 2018, when the market prices of virtual currency declined. At that time, some companies had to withdraw from the mining business.