Hashrate means the summarized computing power of all mining hardware, that is used in the network.
Hashrate can be expressed in the next measure units:
Exahash (EH/s) - full power of the bitcoin network is 6 EH
Because mining gets harder over the time, it’s almost unreal to see units such as “hash per second” in modern blockchain networks. For solving these problems nowadays you need to have hardware with computing power that is much bigger, starting at tens “megahashes per second”.
For example, processor power in size of 10 MH/s means that it can generate as much different combinations as 10 million, among all these combinations there might be the one that will fit all the parameters specified by the network.
What the hashrate depends on?
Hashrate depends on a few most important factors, including which algorithm is used for mining coins. For example, some hardware shows very good results inside the networks with the SHA algorithm (bitcoin, namecoin, peercoin and others), but they won’t be even a bit efficient in networks that use SCRYPT (Litecoin, Dogecoin, Gridcoin and others).
Hardware specs are no less important, these can be very different from one producer to another. Those, who’d like to start mining are recommended to learn more about characteristic of most hardware that is on the market at first, it might help you find the most suitable and profitable option.
You should also keep in mind the cryptocurrency itself: the more it’s popular, the more miners are interested in working for it. They connect their computing powers to the network, what makes its hashrate and, sequently, the mining difficulty bigger.