Testnet: Testing Playground
This network is similar to the main network and has all the same features
The coins mined on this network is meant to be worthless
All of Bitcoin Core functionality works on the testnet
The min difficult on the testnet is half of the mainnet
There is no incentive for miners to mine on the testnet
So users take advantage of this to not include users block and disrupt the network
Signet: Proof of Authority Testnet
It is a test network where each block should contain proof that the block was created by a trusted authority
On testnet anyone could mine on signet only authorized users can mine
Users can create their own signet whenever they want
The script that determines the authorized users is called the challenge script
Regtest: Local Blockchain
Regtest stands for Regression Testing
It is an Bitcoin Core feature that allows us to create a local blockchain
They are used to run closed local testing (no other users)