A master public keys is something different which is usually not derived from a "normal" private key. Better not confuse the terms.

You can learn here about ordinary public keys: https://learnmeabitcoin.com/beginners/guide/public-keys/

A somewhat deeper dive into keys: https://learnmeabitcoin.com/technical/keys/

HD wallets are covered in more detail here: https://learnmeabitcoin.com/technical/keys/hd-wallets/