A postcard refers to a commercially printed card having space on one of its sides, for short messages including the address and the postage stamp. As the name denotes, post cards are sent through the postal services, and come with various types of bright pictures on one of its two sides. The shape of postcards is typically rectangular and they are made of thick paper or thin cardboard. The specialty of postcards lies in the advantage, of the flexibility of posting them without envelopes. The space of attaching postal stamps on the other side of the picture is sufficient enough for postal purposes, making them attractive and comparatively cheaper than the postal charges of sending an envelope.

Postcards are distinguished from postal cards by the fact that postal cards have postage charges pre-printed on them whereas postcards require stamps for posting them. Post cards are generally manufactured and printed by private organizations whereas the concerned postal authority issues the postal cards. Postcards can be designed in various ways and thus considered as an art form. Postcards may involve a detailed study about them, which combined with the study of postcard collection is known as 'Deltiology'.

On the other hand, according to computing terms, a postcard is one that reports 'POST' (Power On Self Test card) error codes. These cards are available in ISA, PCI, AGP and parallel port variants, and are easy to use once inserted into an expansion slot. A book of errors, explaining the error reported and covering a wide range of codes, accompanies these cards. Technicians use these cards quite often for troubleshooting, and booting computers, or to diagnose problems in the hardware.

Several online postcard-designing services are available to order for custom-made postcards, using their designing services or individual artwork. Prices are decided according to the quantity of the order, and other services such as printing, mailing, or shipping charges.