Like any other network, blockchain networks need infrastructure to operate securely and efficiently.
A bitcoin halving (sometimes ‘halvening’) is an event where the reward for mining new blocks is halved, meaning miners receive 50% fewer bitcoins for verifying transactions.
A mainnet is the main blockchain network for a project to run on after rounds of testing on the testnet. It is deemed as the final product of a project and the realization of the promise made in the white paper.