Pseudorandom

A definite function's ability to provide results that pass statistical tests for randomness is referred to as pseudorandom.

Testnet

An alternative blockchain used by developers for testing.

Mainnet

A mainnet is a separate blockchain that operates on its own network using its own protocol and technologies.

Candidate Block

In a few words, a candidate block is a block that a mining node (miner) is trying to mine in order to receive the block reward. So a candidate block may be described as a temporary block that will be either validated or discarded by the network. Miners compete with each other to validate the next block and add it to the blockchain, but first, they have to create a candidate block to participate in the mining competition.