Bitcoin hashrate

To understand Bitcoin hashrate we must first review "Bitcoin mining".

A crash course in Bitcoin mining

While banks validate transactions by controlling the books, blockchains rely on something called a consensus mechanism: a set of rules to ensure all transactions are legitimate. 

Bitcoin’s consensus mechanism works like this:

• New transactions are bundled together and encrypted with a secret 
64-digit number. This is called a “hash”.
• Powerful computers, also known as “miners”, race to discover this number by making billions of random guesses.
• Once the correct guess is made, transactions are recorded on the blockchain with the hash as its unique identifier.