What is the Ethereum network and how many Ethereum networks are you familiar with Blockchain?

In Blockchain, mining is a process to validate transactions by solving a difficult mathematical puzzle called proof of work. Now, proof of work is the process to determine a number (nonce) along with a cryptographic hash algorithm to produce a hash value lower than a predefined target. The nonce is a random value that is used to vary the value of hash so that the final hash value meets the hash conditions.