Recovery seed is a mnemonic code made of 12, 18 or 24 words depending on your choice. This seed is generated the first time you run TREZOR and will help you recovering it’s contents (private keys, bitcoin balance, and transaction history) into a new device if you lose your TREZOR.
PIN is a number that you set when you first run TREZOR. It protects TREZOR against being used by unauthorized persons. We have invented a secure way of entering the PIN so it can’t be keylogged and misused.
Encryption passphrase can be set on top of the PIN. This protects the device in case of a seizure. It’s using military-grade encryption of the seed on TREZOR storage, so even torturing the device in a laboratory won’t leak your private keys.
A combination of these security mechanisms makes your bitcoin ownership with TREZOR absolutely safe
Source: Official website of Trezor – https://trezor.io