A cryptocurrency wallet or simply wallet is a software application or hardware device that is used to receive and send cryptocurrencies. Unlike real-world wallet, a cryptocurrency wallet doesn't hold any cryptocurrencies. Instead, it stores a small secret in the form of a seed (or individual private keys), which is used to generate addresses for incoming transactions and to authorize outgoing transactions.
See also: cryptocurrency bank
Types of wallets 
There are several types of cryptocurrency wallets. They differ in essential properties like security, privacy, interoperability, ease of use or cryptocurrency support. Based on the security, it is possible to divide cryptocurrency wallets into the following groups: less secure software wallets and more secure hardware wallets.
Wallets also differ in how they handle backups. A hierarchical deterministic wallet has to be backed up only once using a recovery seed, while non-deterministic wallets must be backed up each time a new private key is created.
What type of wallet is Trezor?
Trezor is a secure hierarchical deterministic hardware wallet with an easy-to-use Trezor Wallet browser interface and wide cryptocurrency support. Although Trezor is controlled from the Wallet, the seed never leaves the Trezor device, ensuring that there is no risk of losing funds even if the Trezor is exposed to a potentially infected computer.