Hardware wallets are physical devices which securely generate and store Private/Public key-pairs and by extension, addresses. These devices are designed with a component that handles the secure generation of keys, and is never exposed to an internet connection. Signing of transactions happens inside this sequestered portion of the device, and only the resulting outcome, the signature, is broadcast to the network.
It is for this reason that hardware wallets are considered to be the preferred method for most people to manage their cryptocurrency holdings, as it strikes a decent balance between security and accessibility.
There are currently only 2 major hardware wallet manufacturers that have gained wide adoption in the market, Trezor and Ledger which both maintain support for the Ubiq network.
Generally, both brands of device work in a relatively similar way, with the user manipulating the device to confirm actions performed on a separate computer. Differences between the brands is seen in implementations such as whether they use coin-specific applets, if PIN numbers are entered exclusively on-device or not, and style.
Both the Trezor and Ledger brands offer more than one type of device. Usually a more simple and essential model, and another with the more modern and high end features.
If you own a hardware wallet from either of these manufacturers, you can find instructions for using them with Ubiq in the User Guides portion of this documentation.