Blockchain is the foundation for cryptocurrencies such as Etherium and Bitcoin. A blockchain is a system for recording transactions on the network.
Cryptocurrency is mined by having a computer process complex computations to verify transactions.
A cryptocurrency rig is simply a computer that has been set up for mining. There are two common types of crypto mining rigs.
Mining cryptocurrency is not banned or illegal in most countries, including the USA. However, there are countries where it has been made illegal, most notably in China.
The payout of cryptocurrency mining depends a lot on the power of your mining rig. The current reward is 6.25 BTC per block.