Account public key
A public key is a cryptographic code that allows a user to receive cryptocurrencies into his or her account. The public key coupled with the private key are significant tools required to ensure the security of the crypto economy.
XPUB is a master public key used to generate all addresses for an account in a hierarchical deterministic wallet (both already used and unused). As the XPUB key is a public key, it does not allow people to spend funds, but it does make it possible to listen in on all the transactions and balances connected to it.
XPUB and Trezor
As Trezor is an HD wallet, it uses XPUB to generate all the public addresses for a given wallet. To learn how to display account private keys in Trezor Wallet, see Displaying account public key (XPUB).
The XPUB can be used to generate a watch-only wallet in a number of third-party wallets and services. For more information, see Compatible third-party wallets and services.