Wallet interface is an online interface that allows users to set up their device (in case of a hardware wallet interface), manage their cryptocurrency funds, initiate money transfers and interact with third-party apps. Hardware wallet interface is not a real cryptocurrency wallet, because it does not hold or process the seed or private keys. It is merely software that works with non-critical information as accounts and addresses, displays transaction history and communicates users instructions to a hardware device.
There are various wallet interfaces compatible with Trezor. Trezor Wallet is a default and easy-to-use browser interface powered by SatoshiLabs. There are also 3rd-party interfaces for Trezor like Mycelium for Android or Electrum for PC.