It's a Bitcoin wallet that can be used offline. It stores your private keys and understands how to sign a transaction without requiring you to use the internet. It looks to provide you the best of both worlds, as it functions as a highly secure cold storage device while also allowing you to be flexible when it comes to spending your money. The device is so little that you may carry it on your keychain or even in your pocket.
My participation in the TREZOR One was really delightful. The setup was straightforward, the device is intuitive, and the safety measures look to be quite effective. I was also somewhat taken aback by the organization's personnel.