As I understand it and if my answer is incorrect, please correct me, a hardware wallet is a physical device that stores cryptographic keys used to access cryptocurrencies. It is considered to be the safest way to store cryptocurrencies compared to software wallets because of its offline storage and advanced security features.

The primary information that is stored in a hardware wallet is the private key. A private key is a unique secret code that is used to access and control cryptocurrencies. With the private key, users can sign transactions and make transfers from their cryptocurrency accounts. The private key is generated by the wallet when it is set up and is stored securely on the device.
Hardware wallets also store the public key, which is used to receive cryptocurrencies. The public key is similar to a bank account number, and other users can send cryptocurrencies to this address.

Additionally, most hardware wallets also have backup and recovery features that allow users to easily recover their private keys if the device is lost or damaged. The backup phrases are usually a series of words that are stored on a piece of paper or other physical medium and kept in a secure location.

Overall, a hardware wallet stores the critical cryptographic keys that enable the user to send and receive cryptocurrencies, and protects these cryptographic keys with advanced security measures, including offline storage and encryption.