Hash function

SHA

its advisable not to use same public key again for transaction. Always create new pairs.

concept of China running their own chain

by blocking the chineese internet and the miners in China will continue working on their own Chain in parallel and this chain never gets merged with the real Bitcoin blockchain. Can be a possibility.

MH/s

Million Hashes per second

GPUs and ASICS (application specific integrated circuits)

concept of mining pools

mining pool operator vs miners (operator charges 1-3% for making life easier for miners)

what exactly operator is doing here ?

difficulty of mining

number of leading zeros

difficulty of mining increases every 2 weeks

we are still talking about proof of work