Updated: Jun 26, 2020
The Coldcard Wallet is a device that allows users to store and secure their Bitcoin entirely offline - preventing theft by hackers.
A PBST allows you to set up a transaction on your computer - amount & destination - place it on an SD card, and insert it into your Coldcard for approval. Once approved, the SD card goes back to the computer to be broadcast onto the Bitcoin network. Let me reiterate: You can send Bitcoin without your private keys (credentials that allow you to send coins) EVER touching an internet connected device.
The Coldcard Wallet was created by Rodolfo Novak from Coinkite, the same guy who brought you a little device called the OpenDime - a trustless way to physically give someone Bitcoin offline.
Enjoy this tutorial which covers initial setup, importing to Wasabi, and sending/receiving both normally & via PBST.
Step by step video tutorial: