PUBLIC KEY ~ Like a bank account number for receiving bitcoin.

You can give it to people to send you bitcoin, just like you would give your account number to someone so they can send you fiat.

PRIVATE KEY ~ For securing, accessing and sending bitcoin, like the key to a safety deposit box.

A bitcoin private key is a secret string of numbers and letters that allows you to send/spend your bitcoin.

Only you have a copy. It is very important to keep it very safe and secure, as anyone who obtains a copy can spend your bitcoin.

DISTRIBUTED LEDGER ~ A ledger maintained by everyone who wishes to help maintain it.

Instead of a centrally-controlled ledger that is invisible to the public, like one that a bank maintains, Bitcoin is a transparent, open, decentralized ledger visible to anyone, anytime.

The addresses are strings of letters and numbers, with no names attached.

While pseudonymous, it is possible to track transactions, especially if the bitcoin was bought from a centralized KYC exchange.

The Bitcoin network is trustless and anyone can audit it anytime, unlike a bank where one must trust that the ledgers are being kept honestly.