Public key / xpub

The secret number that authorises spending. Whoever has it controls the coins.

A text that fully describes how a wallet derives its addresses; essential backup for multisig.

Multisig means a payment needs several keys out of a set, for example any 2 of 3. Losing one key, or having one stolen, does not lose the coins.

What you share to receive bitcoin. Modern ones start with bc1. Use a new one each time for privacy.