Postcards are one of the most popular marketing tools, whether mailed or left on display. Postcards have a broad range of sizes, as well as different stocks, and are used to convey your message to your customers easily. They can be printed 1 or 2-sided and are often mailed to advertise a product or service. By mailing them you can reach a specific audience. For artists and designers they are great product to sell retail for souvenirs.
To add a convenience to the digital world, consider adding a QR code to your design to link directly to additional online information. This way you can provide more information about your products and services to your intended audience. A QR code can also link to an online message.